Aqueous vinyl polymer coating compositions

ABSTRACT

An aqueous coating composition comprising a crosslinkable water-dispersible vinyl oligomer(s) wherein said composition when drying to form a coating has an open time of at least 20 minutes, a wet edge time of at least 10 minutes, a tack free time of ≦20 hours and an equilibrium viscosity of ≦5,000 Pa·s at any solids content when drying in the range of from 20 to 55 wt % using any shear rate in the range of from 9±0.5 to 90±5 s −1  and at 23±2° C.

FIELD OF THE INVENTION

The present invention relates to certain aqueous ambient temperaturecrosslinkable and shelf stable vinyl polymer compositions which providecoatings having, inter alia, improved open and wet edge times as well asgood tack-free times.

DESCRIPTION OF THE RELATED ART

A general need when applying a decorative or protective coating to asubstrate is to be able to repair irregularities in the still-wetcoating after some time has elapsed, for example by re-brushing over afreshly coated wet substrate, or by applying more of the coatingcomposition over a previously coated substrate either over the main areaof the coating or an edge of the coating or even blending a drop intothe coating without in such case vitiating the complete merging of anyboundaries in the vicinity of the repaired irregularity. Traditionallycompositions containing binder polymers dissolved in organic solventsare used and the organic solvents are employed to modify the dryingcharacteristics of the coated composition. For example, organicsolvent-based alkyds with an open time of 30 to 45 minutes are availablein the decorative “Do-it-Yourself” (DIY) market. However thedisadvantage of organic solvent based coatings is the toxic andflammable nature of such solvents and the pollution and odour caused onevaporation as well as the relatively high cost of organic solvents.

Thus with the continuing concern about the use of organic solvent-basedcoating compositions there has been a long felt need for an aqueouscoating compositions with comparable properties to those achievableusing organic solvent based compositions.

Unfortunately, aqueous polymer coating compositions currently known tothe art do not offer a combination of drying properties which would makethem fully comparable (or even superior to) solvent-based coatings, andin particular do not provide desirably long open and wet edge times (asdiscussed above and also later) together with desirably short tack-freetimes (discussed later).

Thus, very commonly, aqueous-based polymer coating compositions employdispersed high molecular weight polymers as the binder materialsthereof. This results in, inter alia, a short wet edge time when thecoating composition is dried because the dispersed polymer particlestend to coalesce in the edge region of an applied coating very soonafter a wet coating has been applied (probably due to the maximumpacking fraction of the polymer particles having been reached) to form acontinuous film, and since the polymer of this film is of high viscositybecause of the high molecular weight, the lapping (i.e. wet edge) timeof the composition is poor.

It has been shown by viscosity measurements taken during drying thatexisting alkyd emulsions have a high viscosity phase inversion peakduring drying. (Phase inversion is defined as the transition from abinder in a continuous water phase to water in a continuous binder phasewhich occurs during drying). The consequence is a difficulty inre-brushing which starts a few minutes after application of the coating.

It is known from the prior art that longer wet edge or open time isachievable by using solution-type aqueous oligomers (U.S. Pat. No.4,552,908) which can be diluted with large amounts of solvent(s) inorder to create a low viscosity continuous phase during drying of thefilm. However, these systems have high Volatile Organic Contents (VOC's)and are generally unacceptably water-sensitive.

Open time can also be prolonged by using evaporation suppressants (suchas e.g. eicosanol), as described in for example EP 210747. However,water sensitivity is also a problem in this case. Moreover, the wet edgeopen time is insufficiently improved by using such evaporationsuppressants.

From the literature it is also known that open time is easily prolongedby using low solids contents in the aqueous polymer compositions, butthis generally results in the need to apply many layers of paint (forgood opacity). In addition the wet edge time is generally onlymoderately influenced by reducing solids content of an aqueous coatingcomposition with water.

Longer times for repairing irregularities can be achieved by employingaqueous polymer coating compositions in which the binder polymers havevery low viscosities. However, hitherto, a problem with using such lowviscosity polymer binders, is that the resultant coatings have a slowdrying rate, resulting in the coating remaining tacky for anunacceptably long time. A coating should preferably also drysufficiently quickly to avoid the adherence of dust and to ensure thatthe coating quickly becomes waterproof (in case of outdoorapplications), and as discussed above quickly becomes tack-free.

Indeed, the difficulty in developing aqueous polymer coatingcompositions having a desirable combination of drying properties whencoated onto a substrate has been particularly discussed in a recentinterview given by Professor Rob van der Linde (Professor of CoatingsTechnology, University of Technology, Eindhoven, NL) and Kees van derKolk (Sigma Coatings) and reported in “Intermediair” Oct. 6, 1999,35(23), pages 27–29. In this interview concerning environmentallyfriendly paints, there is described the problem of applying aqueouspaints where even the professional painter has little enough time tocorrect any irregularities when needed. This is contrasted (in theinterview) with solvent-based paints (e.g. alkyd paints) which areworkable for a much longer time but have the disadvantage that theorganic solvents forming a major component of such compositions aretoxic and expensive. The interview also mentions that in the comingyears, three universities will cooperate in a project to overcome thedrying disadvantage of aqueous paints. Thus the interview emphasises thecurrent and continuing need and desirability for achieving aqueouspolymer coatings compositions having improved drying properties.

The open time for a coating composition is, in brief, the period of timethat the main area (the bulk) of an applied aqueous coating remainsworkable after it has been applied to a substrate, in the sense thatduring this period re-brushing or application of more coating over themain area of a freshly coated wet substrate is possible without causingdefects such as brush marks in the final dried coating. (A more formaldefinition of open time is provided later in this specification).

The wet edge time for a coating composition is, in brief, the period oftime that the edge region of an applied aqueous coating remains workableafter it has been applied to a substrate, in the sense that during thisperiod re-brushing or application of more coating over the edge regionof a freshly coated wet substrate is possible without causing defectssuch as lap lines in the final dried coating. A more formal definitionof wet edge time is provided later in this specification.

EP 425085 discloses water based autoxidisable coating compositionscomprising a partially esterified carboxylic acid functional filmforming copolymer derived from olefinically unsaturated monomers; istaught therein that it is essential for all or most of the autoxidisablegroups to be 3-allyloxy-2-hydroxypropyl groups (or the 3-alkylallyl orbutyl analogues), in order for the copolymer to retain a high degree ofwater solubility. This approach however is expected to result in thefinal coating having inadequate water resistance for many applicationsand additionally not to give the long open times and lapping timescharacteristic of solvent borne paints. Still further, while acomparative example employs fatty acid groups in the copolymer (apreferred characteristic of the present invention—see later) it hasunacceptably high viscosity.

U.S. Pat. No. 5,422,394 is a further development of the teaching of EP425085 in which the water sensitivity of the final coating is said to bereduced by limiting the concentration of neutralising cations requiredto solubilise the film forming polymer. Nevertheless this modificationdoes not reduce the water sensitivity to an acceptable level or to thelevel of existing solvent borne paints because of the water solubilityof the copolymer.

U.S. Pat. No. 5,270,380 discloses an aqueous composition containing acombination of a latex polymer and a modifying compound where themodifying compound and the latex polymer contain groups which arereactable with each other prior to coating a substrate with thecomposition. However the maximum open time achieved by this method wasonly 15 minutes which is not considered to be sufficient for themajority of coating applications.

U.S. Pat. No. 6,040,368 discloses an aqueous coating composition with anextended open time, the composition including an emulsion polymer with apendant acetate or acetamide groups, a polyether amine and an alkylpolyglycoside. However, no open times greater that 10 minutes wereachieved.

U.S. Pat. No. 4,386,180 discloses a water-based composition comprisingan acrylic latex and a drying oil with an open time of 1 to 3 minuteswhich is clearly not long enough for most coating applications.

U.S. Pat. No. 4,139,514 discloses the addition of water-soluble, acidrich oligomer to a latex to give an open time in excess of 20 minutes.However, this patent is limited to using an alkali-soluble oligomerwhich will result in high water sensitivity of the final coating, thusrequiring an additional curing step at a high temperature

U.S. Pat. No. 4,552,908 describes low molecular weight polymersstabilised with anionic or cationic groups in combination with non-ionicgroups which can contain crosslinking groups like autoxidisable groups(although these are not exemplified). A variety of low molecular weightpolymers are described including vinyl polymers. These polymers must befilm forming and contain acid and a wet edge time of >10 minutes isdescribed. However, the combination of properties such as claimed in thepresent invention (see later) is not described. All the oligomersmentioned in this patent are water soluble as in EP 425085 and U.S. Pat.No. 5,422,394, and so will also be water sensitive in final application.Furthermore, there is no mention of oligomer in combination with adispersed polymer, which is a preferred feature of the present invention(see later).

BRIEF SUMMARY OF THE INVENTION

We have now invented aqueous polymer coating compositions having a veryadvantageous combination of properties, particularly with regard to opentime, wet edge time, and tack-free time as discussed above, and which(surprisingly in view of comments by van der Linde and van der Kolk)avoid the drawbacks of the currently available composition.

According to the present invention there is provided an aqueous coatingcomposition comprising a crosslinkable water-dispersible vinyloligomer(s) wherein said composition when drying to form a coating hasthe following properties:

i) an open time of at least 20 minutes;

ii) a wet-edge time of at least 10 minutes;

iii) a tack-free time of ≦20 hours;

iv) 0 to 25% of co-solvent by weight of the composition; and

v) an equilibrium viscosity of ≦5,000 Pa·s, at any solids content whendrying in the range of from 20 to 55% by weight of the composition,using any shear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2°C.

DETAILED DESCRIPTION OF THE INVENTION

Open time is more formally defined as the maximum length of time, usingthe test method and under the specified conditions described later inwhich a brush carrying the aqueous composition of the invention can beapplied to the main area of a coating of the aqueous composition of theinvention after which the coating flows back so as to result in ahomogenous film layer.

Preferably the open time is at least 25 minutes, more preferably atleast 30 minutes and most preferably at least 35 minutes.

Wet edge time is more formally defined as the maximum length of time,using the test method, under the specified conditions described herein,in which a brush carrying the aqueous composition of the invention canbe applied to the edge region of a coating of the aqueous composition ofthe invention after which the coating flows back without leaving any laplines so as to result in a homogenous film layer.

Preferably the wet-edge time is at least 12 minutes, more preferably atleast 15 minutes most preferably at least 18 minutes and especially atleast 25 minutes.

The drying process of an invention composition can be divided into fourstages namely the period of time necessary to achieve, respectively,dust-free, tack-free, sandable and thumb-hard coatings using the testmethods described herein.

Preferably the dust free time is ≦4 hours, more preferably ≦2 hours andmost preferably ≦50 minutes.

Preferably the tack-free time is ≦15 hours, more preferably ≦12 hoursand most preferably ≦8 hours.

Preferably the thumb hard time is ≦48 hours, more preferably ≦24 hours,most preferably ≦16 hours and especially ≦10 hours.

Preferably the resultant coating is sandable within 72 hours, morepreferably within 48 hours, still more preferably within 24 hours andespecially within 16 hours.

A co-solvent, as is well known in the coating art, is an organic solventemployed in an aqueous coating composition to improve the dryingcharacteristics thereof.

The co-solvent may be solvent incorporated or used during preparation ofthe vinyl oligomer(s) or may have been added during formulation of theaqueous composition.

The equilibrium viscosity of the aqueous coating composition whenmeasured under the conditions as described above, is a suitable methodfor illustrating the drying characteristics of the aqueous coatingcomposition. By the equilibrium viscosity of an aqueous composition at aparticular shear rate and solids content is meant the viscosity measuredwhen the aqueous composition has been subjected to the shear rate forlong enough to ensure that the viscosity measurement has reached aconstant value.

If the composition is to remain brushable and workable during drying sothat it has the desired open time and wet edge time, it is necessarythat its equilibrium viscosity does not exceed defined limits during thedrying process and hence over a range of solids contents. Accordinglythe crosslinkable water-dispersible vinyl oligomer(s) which are used inthis invention do not give a significant phase inversion viscosity peak,if any at all, during the drying process when the system inverts fromone in which water is the continuous phase to one in which thecrosslinkable water-dispersible vinyl oligomer(s) is the continuousphase.

The shear rate to measure the equilibrium viscosity is preferably anyshear rate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferablyany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹.

Preferably the equilibrium viscosity of the aqueous coating compositionof the invention is ≦3000 Pa·s, more preferably ≦1500 Pa·s, still morepreferably ≦500 Pa·s, especially ≦100 Pa·s and most especially ≦50 Pa·swhen measured as defined above.

Preferably, the composition of the invention has an equilibriumviscosity ≦5,000 Pa·s when measured using any shear rate in the range offrom 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦3,000 Pa·swhen measured using any shear rate in the range of from 0.9±0.05 to 90±5s⁻¹, and an equilibrium viscosity of ≦1,500 Pa·s when measured using anyshear rate of from 9±0.5 to 90±5 s⁻¹, at any solids content when dryingin the range of from 20 to 55% by weight of the composition and at 23±2°C.

More preferably, the composition of the invention has an equilibriumviscosity of ≦3,000 Pa·s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦1,500Pa·s when measured using any shear rate in the range of from 0.9±0.05 to90±5 s⁻¹, and an equilibrium viscosity of ≦500 Pa·s when measured usingany shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solidscontent when drying in the range of from 20 to 55% by weight of thecomposition and at 23±2° C.

Most preferably, the composition of the invention has an equilibriumviscosity of ≦1500 Pa·s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦200Pa·s when measured using any shear rate in the range of from 0.9±0.05 to90±5 s⁻¹, and an equilibrium viscosity of ≦100 Pa·s when measured usingany shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solidscontent when drying in the range of from 20 to 55% by weight of thecomposition and at 23±2° C.

Preferably the equilibrium viscosity of the composition of the inventionis ≦5000 Pa·s, more preferably ≦3000 Pa·s when measured using any shearrate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferably usingany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹; after a 12%,preferably a 15% and most preferably an 18% increase in the solidscontent by weight of the composition when drying.

A 12% increase in the solids content by weight of the composition meansfor example going from a solids content of 35 to 47% by weight of thecomposition.

Preferably the solids content of the aqueous coating composition whendetermining the equilibrium viscosity is in the range of from 20 to 60%,more preferably in the range of from 20 to 65%, still more preferably inthe range of from 20 to 70% and especially in the range of from 20 to75% by weight of the composition.

In a preferred embodiment of the present invention said vinyloligomer(s) has a solution viscosity ≦150 Pa·s, as determined from a 80%by weight solids solution of the crosslinkable vinyl oligomer(s) in atleast one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.

A choice of solvents for determining the solution viscosity of the vinyloligomer(s) is provided herein because the nature of the vinyloligomer(s) may affect its solubility.

Preferably the solution viscosity of the crosslinkable vinyl oligomer(s)is ≦100 Pa·s, especially ≦50 Pa·s and most especially ≦30 Pa·s whenmeasured as defined above.

Alternatively in this embodiment of the invention, and more preferably,the solution viscosity of the vinyl oligomer(s) may be measured at 23±2°C., and the crosslinkable vinyl oligomer(s) may thus also be describedas preferably having a solution viscosity ≦250 Pa·s, as determined froma 70% by weight solids solution of the crosslinkable vinyl oligomer(s)in a solvent mixture consisting of:

i) at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof;

ii) water and

iii) N,N-dimethylethanolamine;

where i), ii) and iii) are in weight ratios of 20/7/3 respectively,using a shear rate of 90±5 s⁻¹ and at 23±2° C.

Preferably in the preceding alternative the solution viscosity of thevinyl oligomer(s) is ≦100 Pa·s, more especially ≦50 Pa·s, still moreespecially ≦35 Pa·s and most especially ≦20 Pa·s, when measured asdefined herein at 23±2° C.

If a mixture of N-methylpyrrolidone (NMP) and n-butylglycol (BG) isused, preferably the ratio of NMP:BG is in the range of from 0.01:99.9to 99.9:0.01, more preferably the ratio of NMP:BG is in the range offrom 0.01:99.9 to 10:90 and in the range of from 90:10 to 99.9:0.01, andmost preferably the ratio of NMP:BG is in the range of from 0.5:99.5 to5:95 and in the range of from 95:5 to 99.5:0.5.

In a special embodiment of the present invention the wet edge time inminutes of the aqueous coating composition is at least Q/(wt. % solidsof the aqueous coating composition)^(0.5), wherein the solids content ofthe aqueous coating composition is between 15 and 70 wt. %, morepreferably between 30 and 65 wt. % and most preferably between 40 and 60wt. % and Q is a constant of 84 more preferably of 100, most preferablyof 126 and especially of 151.

The crosslinkable vinyl oligomer(s) may crosslink at ambient temperatureby a number of mechanisms including but not limited to autoxidation,Schiff base crosslinking and silane condensation. By crosslinking byautoxidation is meant that crosslinking results from oxidation occurringin the presence of air and which usually involves a free radicalmechanism and is preferably metal-catalysed, resulting in covalentcrosslinks. By Schiff base crosslinking is meant that crosslinking takesplace by the reaction of a carbonyl functional group(s) where by acarbonyl functional group herein is meant an aldo or keto group andincluding an enolic carbonyl group such as is found in an acetoacetylgroup, with a carbonyl-reactive amine and/or hydrazine (or blocked amineand/or blocked hydrazine) functional group. Examples ofcarbonyl-reactive amine (or blocked amine) functional groups includeones provided by the following compounds or groups: R—NH₂, R—O—NH₂,R—O—N═C<, R—NH—C(═O)—O—N═C< and R—NH—C(═O)—O—NH₂ or blocked hydrazinewhere R is optionally substituted C₁ to C₁₅, preferably C₁ to C₁₀alkylene, optionally substituted alicyclic or optionally substitutedaryl or R may also be part of a polymer. Examples of carbonyl-reactivehydrazine (or blocked hydrazine) groups include R—NH—NH₂,R—C(═O)—NH—NH₂, R—C(═O)—NH—N═C<, R—NH—C(═O)—NH—NH₂ andR—NH—C(═O)—NH—N═C< where R is as described above. By silane condensationis meant the reaction of alkoxy silane or —SiOH groups in the presenceof water, to give siloxane bonds by the elimination of water and/oralkanols (for example methanol) during the drying of the aqueous coatingcomposition.

Preferably the crosslinkable vinyl oligomer(s) is a self-crosslinkablevinyl oligomer(s) (i.e. crosslinkable without the requirement for addedcompounds which react with groups on the vinyl oligomer(s) to achievecrosslinking, although these can still be employed if desired).Preferably the crosslinking is by autoxidation, optionally incombination with other crosslinking mechanisms as discussed herein.Suitably autoxidation is provided for example by fatty acid groupscontaining unsaturated bonds (by which is meant the residue of eachfatty acids of which have become incorporated into the vinyl oligomer byreaction at their carboxyl (groups) or by (meth)allyl functionalresidues, β-keto ester or β-keto amide groups. It may also be provided(at least in part) by terminal unsaturated bonds in the vinyloligomer(s) if made using a catalytic chain transfer polymerisationprocess as discussed later. Preferably autoxidation is provided at leastby fatty acid groups containing unsaturated bonds and, in cases where(meth)allyl groups are used, it is preferred that the ratio unsaturatedfatty acid groups to (meth)allyl groups is ≧2:1, more preferably ≧3:1,and still more preferably ≧5:1; most preferably, however, no (meth)allylgroups are present.

Preferably the concentration of unsaturated fatty acid groups (ifpresent) in the autoxidisably crosslinkable vinyl oligomer(s) is 10 to80%, preferably 12 to 70%, most preferably 15 to 60% by weight based onthe weight of the vinyl oligomer(s). If combined with otherautoxidisable groups in the aqueous coating composition, the fatty acidgroup content may more readily be below 10% by weight of the vinyloligomer(s). For the purpose of determining the fatty acid group contentof the vinyl oligomer(s), it is convenient for practical purposes to usethe weight of the fatty acid reactant including the carbonyl group butexcluding the hydroxyl group of the terminal acid group of the fattyacid. Suitable unsaturated fatty acids for providing fatty acid groupsin the vinyl oligomer(s) include fatty acids derived from vegetable andnon-vegetable oil such as soyabean oil, palm oil, linseed oil, tung oil,rapeseed oil, sunflower oil, tallow oil, (dehydrated) castor oil,safflower oil and fatty acids such as linoleic acid, linolenic acid,palmitoleic acid, oleic acid, eleostearic acid, licanic acid,arachidonic acid, ricinoleic acid, erucic acid, gadoleic acid,clupanadonic acid and/or combinations thereof. Particularly preferred isa vinyl oligomer(s) in which the autoxidisable groups are derived onlyfrom unsaturated fatty acids. Preferably at least 40% by weight, morepreferably at least 60% by weight of the unsaturated fatty acid groupscontain at least two unsaturated groups.

Other crosslinking mechanisms known in the art include those provided bythe reaction of epoxy groups with amino, carboxylic acid or mercaptogroups, the reaction of mercapto groups with ethylenically unsaturatedgroups such as fumarate and acryloyl groups, the reaction of maskedepoxy groups with amino or mercapto groups, the reaction ofisothiocyanates with amines, alcohols or hydrazines, the reaction ofamines (for example ethylene diamine or multifunctional amine terminatedpolyalkylene oxides) with β-diketo (for example acetoacetoxy oracetoamide) groups. The use of blocked crosslinking groups may bebeneficial.

The crosslinkable vinyl oligomer(s) may be completely water-soluble oronly have partial or low solubility in water. Preferably thecrosslinkable vinyl oligomer(s) only has partial or little solubility inwater. If the crosslinkable vinyl oligomer(s) is only partially orlittle soluble in water, it preferably has low water solubility in a pHrange of from 2 to 10 and is either self-dispersible in water (i.e.dispersible by virtue of a sufficient concentration of selected bound(in-chain, chain-pendant and or chain-terminal) hydrophilic groups builtinto the vinyl oligomer(s), and thus not requiring high shear techniquesand/or added surfactants to produce the dispersion, although suchmethods can also be included if desired), or is only dispersible inwater with the aid of added (i.e. external) surface active agents and/orthe use of high shear mixing. Low water solubility confers the advantageof a reduced water-sensitivity of the applied coating. Such low watersolubility is defined herein as the crosslinkable vinyl oligomer(s)being less than 70% by weight soluble in water throughout the pH rangeof from 2 to 10 as determined for example by a centrifuge test asdescribed herein. Preferably the crosslinkable vinyl oligomer(s) is≦60%, more preferably ≦50% most preferably ≦30% by weight soluble inwater throughout the pH range of from 2 to 10.

The crosslinkable vinyl oligomer(s) preferably contains a sufficientconcentration of bound hydrophilic water-dispersing groups capable ofrendering the oligomer(s) self-water-dispersible, but the concentrationof such groups is preferably not so great that the oligomer(s) has anunacceptably high water solubility in order to not compromise the watersensitivity of the final coating.

The type of hydrophilic groups capable of rendering the crosslinkablevinyl oligomer(s) self water-dispersible are well known in the art, andcan be ionic water-dispersing groups or non-ionic water-dispersinggroups. Preferably non-ionic water-dispersing groups are used. Preferrednon-ionic water-dispersing groups are polyalkylene oxide groups, morepreferably polyethylene oxide groups. A small segment of thepolyethylene oxide group can be replaced by propylene oxide segment(s)and/or butylene oxide segment(s), however the polyethylene oxide groupshould still contain ethylene oxide as a major component. When thewater-dispersible group is polyethylene oxide, the preferred ethyleneoxide chain length is >4 ethylene oxide units, preferably >8 ethyleneoxide units and most preferably >15 ethylene oxide units. Preferably thepolyethylene oxide group has a Mw from 175 to 5000 Daltons, morepreferably from 350 to 2200 Daltons, most preferably from 660 to 2200Daltons. Preferably the vinyl oligomer(s) has a polyethylene oxidecontent of 0 to 45% by weight, more preferably 0 to 30% by weight andstill more preferably 2 to 20% by weight and especially 3 to 15% byweight.

Preferred ionic water-dispersing groups are anionic water-dispersinggroups, especially carboxylic, phosphonic and or sulphonic acid groups.The anionic water-dispersing groups are preferably fully or partially inthe form of a salt. Conversion to the salt form is optionally effectedby neutralisation of the crosslinkable vinyl oligomer(s) with a base,preferably during the preparation of the crosslinkable vinyl oligomer(s)and/or during the preparation of the composition of the presentinvention. The anionic water-dispersing groups may in some cases beprovided by the use of a monomer having an already neutralised acidgroup in the vinyl oligomer(s) synthesis so that subsequentneutralisation is unnecessary. If anionic water-dispersing groups areused in combination with non-ionic water-dispersing groups,neutralisation may not be required. Alternatively anionic dispersinggroups may also be introduced by using blocked acids like tertiary butylmethacrylate, which can readily be hydrolysed upon dispersion.

If the anionic water-dispersing groups are neutralised, the base used toneutralise the groups is preferably ammonia, an amine or an inorganicbase. Suitable amines include tertiary amines, for example triethylamineor N,N-dimethylethanolamine. Suitable inorganic bases include alkalihydroxides and carbonates, for example lithium hydroxide, sodiumhydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, forexample N⁺(CH₃)₄OH⁻, can also be used. Generally a base is used whichgives counter ions which may be desired for the composition. Forexample, preferred counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ andsubstituted ammonium salts.

Cationic water dispersible groups can also be used, but are lesspreferred. Examples include pyridine groups, imidazole groups and orquaternary ammonium groups which may be neutralised or permanentlyionised (for example with dimethylsulphate).

The crosslinkable vinyl oligomer(s) preferably has a weight averagemolecular weight (Mw) in the range of from 1,000 to 80,000 Daltons, morepreferably in the range of from 1,000 to 50,000 Daltons, still morepreferably in the range of from 1,200 to 30,000 Daltons, and mostpreferably in the range of from 5,000 to 20,000 Daltons. If thecrosslinkable vinyl oligomer(s) is prepared from a reactive precursorvinyl oligomer(s) (see later), then the Mw of the precursor oligomer ispreferably in the range of from 1000 to 20,000 Daltons, more preferablyin the range of from 1000 to 10,000 Daltons, and most preferably in therange of from 1000 to 5000 Daltons.

For the purpose of this invention any molecular species mentioned hereinwith a molecular weight <1000 Daltons is classified as either a reactivediluent or a plasticiser and is therefore not taken into account for thedetermination of the Mw, Mn or PDi. When Daltons are used to givemolecular weight data it should be understood that this is not a truemolecular weight, but a molecular weight measured against polystyrenestandards.

Preferably a significant part of any crosslinking reaction only takesplace after application of the aqueous coating composition to asubstrate, in order to avoid an excessive molecular weight build up inthe invention composition prior to such application (by precrosslinking)which may lead to unacceptably increased viscosity of the aqueouscoating composition on the substrate in the early stages of drying.

The molecular weight limits suitable to obtain the preferred lowsolution viscosity of the crosslinkable vinyl oligomer(s) as definedabove may depend in part on the amount and type of co-solvent if presentin the aqueous composition of the invention. Thus a higher molecularweight limit is possible when there is more co-solvent in thecomposition, and the lower molecular weight preferences are moreapplicable to low or zero co-solvent concentrations. Furthermore, if abranched vinyl oligomer(s) is used, higher molecular weight limits arepreferred as branched structures tend to give a lower viscosity than alinear structure for any given Mw.

The molecular weight distribution (MWD) of the crosslinkable vinyloligomer(s) has an influence on the equilibrium viscosity of the aqueouscomposition of the invention and hence an influence on the open time.MWD is conventionally described by the polydispersity index (PDi). PDiis defined as the weight average molecular weight divided by the numberaverage molecular weight (Mw/Mn) where lower values are equivalent tolower PDi's. It has been found that a lower PDi often results in lowerviscosities for a given Mw crosslinkable vinyl oligomer(s). Preferablythe value of PDi is ≦15, more preferably ≦10, and most preferably ≦5. Ina preferred embodiment of the invention the value of the Mw×PDi^(0.8) ofthe crosslinkable vinyl oligomer(s) is ≦300,000 and more preferably theMw×PDi^(0.8) is ≦220,000. A specific PDi preference for a reactiveprecursor vinyl oligomer(s) (if used—see later) is in the range of from1.1 to 1.9 for Mw's of the resulting crosslinkable vinyl oligomer(s) inthe range of from 1000 to 40,000 Daltons, although normally such lowvalues can only be obtained by very specific synthetic methods. One suchmethod is to utilise catalytic chain transfer polymerisation whenpreparing very low molecular weight polymers (see later), and it hasbeen found that this technique is especially effective for preparing aprecursor vinyl oligomer(s). Another method of preparing vinyloligomer(s) with particularly lower PDi's is to utilise anionicpolymerisation techniques. However this procedure is much less preferredbecause of the high cost and the limitation in monomer types which canbe polymerised by this technique. Alternatively other techniques includethe so called “living” free radical polymerisation techniques such asatom transfer radical polymerisation, group transfer polymerisation,nitroxide mediated polymerisations and RAFT (reversible additionfragmentation chain transfer) polymerisations.

The crosslinkable vinyl oligomer(s) may comprise a single crosslinkablevinyl oligomer or a mixture of crosslinkable vinyl oligomers. Thecrosslinkable vinyl oligomer(s) may optionally be used in conjunctionwith a crosslinkable oligomer(s) of a non-vinyl type which has asolution viscosity within the same preferred limits as the solutionviscosity of the vinyl oligomer(s). Indeed up to 90% by weight of thecrosslinkable oligomer(s) in the invention may be of a non-vinyl type.The crosslinkable oligomer(s) (vinyl-type plus, if present, non-vinyltype) may optionally be used in conjunction with up to 250% by weightthereof of any type of non-crosslinkable oligomer(s) (vinyl and/ornon-vinyl type) provided that the non-crosslinkable oligomer(s) has asolution viscosity within the preferred ranges defined above for thesolution viscosity of the crosslinkable vinyl oligomer(s). In such casesmore preferably up to 120 wt % of the non-crosslinkable oligomer(s)(based on the wt % of crosslinkable oligomer(s)), especially up to 30wt. %, more especially up to 10 wt. % and most especially 0 wt. % isused.

Oligomer(s) of a non-vinyl type include but are not limited to forexample polyurethane oligomer(s), polyester oligomer(s), polyamideoligomer(s), polyether oligomer(s), polycarbonate oligomer(s) and/orpolysiloxane oligomer(s) and the non-vinyl type oligomer(s) mayoptionally be branched, hyperbranched or dendritic.

The crosslinkable vinyl oligomer(s) is usually derived from freeradically polymerisable olefinically unsaturated monomer(s), and cancontain polymerised units of a wide range of such monomers, especiallythose commonly used to make binders for the coatings industry. The freeradically polymerisable olefinically unsaturated monomer(s) may includemonomers which carry for example crosslinker groups or (if to bepresent) hydrophilic water-dispersing groups which thus may beintroduced directly in the vinyl oligomer by free radicalpolymerisation, or alternatively crosslinker groups and (if to be used)hydrophilic water-dispersing groups may be introduced by a reaction of areactive precursor vinyl oligomer using a reactive compound bearing acrosslinker group(s) or a hydrophilic group(s) as the case may be (seelater for more detail). By a vinyl oligomer (or precursor vinyloligomer) herein is meant a homo- or co-oligomer (or homo- orco-precursor oligomer) derived from the addition polymerisation (using afree radical initiated process which may be carried out in an aqueous ornon-aqueous medium) of one or more olefinically unsaturated monomers.Therefore by a vinyl monomer is meant an olefinically unsaturatedmonomer. The vinyl oligomer(s) of the composition of the inventionpreferably has an acid value of in the range of from 0 to 80 mg KOH/g,more preferably in the range of from 0 to 30 mg KOH/g most preferably inthe range of from 10 to 30 mg KOH/g. A particularly preferred vinyloligomer(s) is an acrylic oligomer(s) (i.e. based predominantly on atleast one ester of acrylic or methacrylic acid).

Examples of vinyl monomers which may be used to form a vinyl oligomer(or precursor vinyl oligomer) include but are not limited to1,3-butadiene, isoprene, styrene, α-methyl styrene, divinyl benzene,acrylonitrile, methacrylonitrile, vinyl halides such as vinyl chloride,vinylidene halides such as vinylidene chloride, vinyl ethers, vinylesters such as vinyl acetate, vinyl propionate, vinyl laurate, and vinylesters of versatic acid such as VeoVa 9 and VeoVa 10 (VeoVa is atrademark of Shell), heterocyclic vinyl compounds, alkyl esters ofmono-olefinically unsaturated dicarboxylic acids (such as di-n-butylmaleate and di-n-butyl fumarate) and, in particular, esters of acrylicacid and methacrylic acid of formulaCH₂═CR¹—COOR²wherein R¹ is H or methyl and R² is optionally substituted alkyl orcycloalkyl of 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms)examples of which are methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isopropyl acrylate,isopropyl methacrylate, n-propyl acrylate, n-propyl methacrylate, andhydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate, hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate and their modifiedanalogues like Tone M-100 (Tone is a trademark of Union CarbideCorporation).

Particularly preferred is a vinyl oligomer (or precursor vinyl oligomer)made from a monomer system comprising at least 40 weight % of one ormore monomers of the formula CH₂═CR¹COOR² as defined above. Such apreferred vinyl oligomer (or precursor vinyl oligomer) is defined hereinas an acrylic oligomer (or precursor acrylic oligomer). More preferably,the monomer system contains at least 50 wt. % of such monomers, andparticularly at least 60 wt. %. The other monomer(s) in such acrylicoligomer(s) (if used) may include one or more of the other vinylmonomers mentioned above, and/or may include ones different to suchother monomers. Particularly preferred monomers include butyl acrylate(all isomers), butyl methacrylate (all isomers), methyl methacrylate(all isomers), ethyl hexyl methacrylate, esters of (meth)acrylic acid,acrylonitrile, vinyl acetate and styrene.

The crosslinker groups may, as mentioned briefly above, be introducedinto a vinyl oligomer using two general methods: i) by utilising in thepolymerisation process to form a vinyl oligomer, a vinyl comonomer(s)which carries a crosslinker group; and ii) utilising a precursor vinyloligomer bearing selected reactive groups and which precursor oligomeris subsequently reacted with a compound carrying a crosslinker group andalso a reactive group of the type which will react with the selectedreactive groups on the precursor vinyl oligomer to provide attachment ofthe crosslinker group to the oligomer via covalent bonding. An exampleof i) is the preparation of an adduct of GMA (glycidylmethacrylate) andan unsaturated fatty acid to form a methacrylate bearing an unsaturatedfatty acid residue as a crosslinker group, and then using this as acomonomer in the polymerisation synthesis of the crosslinkable vinyloligomer. An example of ii) is the initial formation of a precursorvinyl oligomer bearing epoxide groups by employing GMA as a comonomer inthe synthesis of the precursor oligomer and then reacting this with anunsaturated fatty acid whereby the acid and epoxide groups react toattach the unsaturated fatty acid residue crosslinker group by covalentbonding.

Other crosslinker groups such as acetoacetoxy groups may be introducedinto a vinyl oligomer by utilising a comonomer such as acetoacetoxymethacrylate in a free radical polymerisation (method (i)) or reacting acompound having a β-diketone group with primary or secondary aminegroups on a precursor vinyl oligomer to form enamines which are alsoeffective as crosslinker groups (method (ii)).

The hydrophilic water-dispersing groups (if present) can be introducedby methods analogous to those for introducing crosslinker groups, forexample i) utilising in the synthesis of the vinyl oligomer(s) a vinylcomonomer which carries a hydrophilic water-dispersing group (forexample an olefinically unsaturated monocarboxylic, sulphonic and/ordicarboxylic acid, such as acrylic acid, methacrylic acid, β-carboxyethylacrylate, fumaric acid or itaconic acid, an amide such as(meth)acrylamide, or a polyethyleneoxide containing (meth)acrylatemonomer such as methoxy(polyethyleneoxide (meth)acrylate) or ahydroxyalkyl (meth)acrylate like hydroxyethyl (meth)acrylate HE(M)A, oralternatively ii) utilising a precursor vinyl oligomer bearing selectivereactive groups which is subsequently reacted with a compound carrying awater-dispersing group and also a reactive group of the type which willreact with the selected reactive groups on the precursor vinyl oligomerto provide attachment of the water-dispersing group to the oligomer viacovalent bonding. An example of the second method (ii) is where an epoxyfunctional reactive precursor oligomer is formed utilising GMA as acomonomer, which precursor oligomer is then reacted with an amineterminated polyethyleneoxide (such as certain members of the Jeffamineseries available from Huntsman) whereby polyethyleneoxide waterdispersing groups become attached to the oligomer. Alternativelyacetoacetoxy ethyl methacrylate (AAEM) instead of GMA can be used tobond the amine terminated polyethyleneoxide to the vinyl oligomer (thereaction then being between acetoacetoxy and amine groups).

The vinyl oligomer(s) may optionally contain other functional groups(i.e. different to those already mentioned above) to contribute to thecrosslinking of vinyl oligomer(s) in the coating. Examples of such othergroups include unsaturated groups provided in the larger context ofmaleic, fumaric, acryloyl, methacryloyl, styrenic and allylic groups andmercapto groups.

The glass transition temperature (Tg) of the precursor vinyl oligomer(s)may vary within a wide range. The precursor vinyl oligomer(s) is thevinyl oligomer(s) before functionalisation with fatty acid groups. TheTg as measured by modulated differential scanning calorimetry (DSC) ispreferably in the range of from −90 to 120° C., more preferably in therange of from −70 to 80° C. Particularly preferred is that the Tg of theprecursor vinyl oligomer(s) is in the range of from −60 to 60° C., morepreferably in the range of from −50 to 30° C.

The crosslinkable vinyl oligomer(s) or (if used) precursor vinyloligomer(s) is preferably prepared by free radical polymerisation,although in some circumstances anionic polymerisation may be utilised.The free radical polymerisation can be performed by techniques known inthe art, for example as emulsion polymerisation, solutionpolymerisation, suspension polymerisation or bulk polymerisation.

If a precursor vinyl oligomer(s) is utilised (i.e. using method (ii)),one preferred technique for preparing it is to perform a solutionpolymerisation in a water-miscible or a water-immiscible solvent. Thistechnique is beneficial because subsequent functionalisation reactionsto introduce the crosslinker groups and, if desired, thewater-dispersing groups can then be conveniently and efficientlyperformed in the solution of the precursor vinyl oligomer. When thesolvent is water-miscible it may aid the subsequent dispersion of thecrosslinkable oligomer in water. The solvent may then be either removedby evaporation or left in the dispersion.

Emulsion polymerisation is a preferred technique when the crosslinkergroups are directly introduced by employing method (i) for example byusing a GMA/fatty acid adduct as a comonomer, since the resultantcrosslinkable vinyl oligomer(s) is then obtained directly in the form ofan aqueous dispersion, avoiding the need for a separate dispersion step.When emulsion polymerisation is employed to make the crosslinkable vinyloligomer(s), it is convenient to also introduce any hydrophilicwater-dispersing groups by a comonomer approach (method (i)).

A free-radical polymerisation of vinyl monomer(s) to form acrosslinkable vinyl oligomer(s) or precursor vinyl oligomer(s) willrequire the use of a free-radical-yielding initiator(s) to initiate thevinyl polymerisation. Suitable free-radical-yielding initiators includeinorganic peroxides such as K, Na or ammonium persulphate, hydrogenperoxide, or percarbonates; organic peroxides, such as acyl peroxidesincluding e.g. benzoyl peroxide, alkyl hydroperoxides such as t-butylhydroperoxide and cumene hydroperoxide; dialkyl peroxides such asdi-t-butyl peroxide; peroxy esters such as t-butyl perbenzoate and thelike; mixtures may also be used. The peroxy compounds are in some casesadvantageously used in combination with suitable reducing agents (redoxsystems) such as Na or K pyrosulphite or bisulphite, and iso-ascorbicacid. Azo compounds such as azoisobutyronitrile may also be used. Metalcompounds such Fe.EDTA (EDTA is ethylene diamine tetracetic acid) mayalso be usefully employed as part of the redox initiator system. It ispossible to use an initiator system partitioning between the aqueous andorganic phases, e.g. a combination of t-butyl hydroperoxide,iso-ascorbic acid and Fe.EDTA. The amount of initiator or initiatorsystem to use is conventional, e.g. within the range 0.05 to 6 wt. %based on the total vinyl monomer(s) used.

As stated above, a preferred feature of the invention is a low solutionviscosity for the vinyl oligomer(s) (as defined) which may be obtainedby controlling the molecular weight and/or the MWD of the crosslinkablevinyl oligomer(s). It may therefore be desirable to add a chain transferagent to the free radical polymerisation process or to use high levelsof initiator, typically above 1% by weight, more preferably above 2% byweight more preferably above 3.5% by weight of vinyl monomer(s) to givethe desired low molecular weight. Conventional chain transfer agents maybe utilised and include mercaptans, sulphides, disulphides,triethylamine and halocarbons. In some instances chain transfer to themonomer(s) or chain transfer to solvents (e.g. toluene) during thepolymerisation is capable of reducing the molecular weight to thedesired value. Examples include polymerisations in which α-methylstyrene or vinyl chloride are used as a comonomer. In particular howeverthe technique known as catalytic chain transfer polymerisation (CCTP)may be used to provide low molecular weights. In this case a freeradical polymerisation is carried out using a free radical forminginitiator and a catalytic amount of a selected transition metal complexacting as a catalytic chain transfer agent (CCTA), and in particular aselected cobalt chelate complex. Such a technique has been describedfairly extensively in the literature within the last twenty years or so.For example, various literature references, such as N. S. Enikolopyan etal, J. Polym. Chem. Ed., Vol 19, 879 (1981), discloses the use of cobaltII porphyrin complexes as chain transfer agents in free radicalpolymerisation, while U.S. Pat. No. 4,526,945 discloses the use ofdioxime complexes of cobalt II for such a purpose. Various otherpublications, e.g. U.S. Pat. No. 4,680,354, EP-A-0196783, EP-A-0199436and EP-A-0788518 describe the use of certain other types of cobalt IIchelates as chain transfer agents for the production of oligomers ofolefinically unsaturated monomers by free-radical polymerisation.WO-A-87/03605 on the other hand claims the use of certain cobalt IIIchelate complexes for such a purpose, as well as the use of certainchelate complexes of other metals such as iridium and rhenium.

The use of catalytic chain transfer agents provide 3 important benefits:

a) very low concentrations of catalytic chain transfer agent (typically1 to 1000ppm by weight of vinyl monomer used) are required to attain thepreferred low molecular weight oligomer. In contrast, conventional chaintransfer agents such as mercaptans need to be added at much higherconcentrations (typically 0.5 to 7% by weight of vinyl monomer) if thedesired molecular weight is to be achieved. Such high concentrations ofchain transfer agent are economically unattractive and may give thefinal product an unacceptable odour. This unpleasant odour is veryapparent in formulated wet systems and during the coating process. Eventhe final dry film can exhibit an unpleasant odour. In contrast when thecrosslinkable vinyl oligomer(s) is prepared using a catalytic chaintransfer agent there is no odour from the chain transfer agent at anystage;

b) a vinyl oligomer(s) prepared by catalytic chain transferpolymerisation (CCTP) contains a terminal unsaturated group on many, ifnot every vinyl oligomer molecule. This terminal unsaturation canparticipate in autoxidation reactions for example in fatty acidcrosslinking systems. Thus the crosslinkable vinyl oligomer(s) of thepresent invention could have autoxidisable crosslinker groups comprisingthe unsaturated groups from fatty acids as well as terminal unsaturatedgroups resulting from CCTP. The capability of the terminal unsaturationto participate in the autoxidative crosslinking reactions may cause thecrosslinking of the vinyl oligomer(s) to be much more efficient i.e. therate and extent of crosslinking may be increased, giving rise to asignificant reduction in drying time and improvement of the mechanicalproperties of the final coating.

c) CCTP allows the preparation of a vinyl oligomer(s) which has anarrower PDi than is achievable by the use of conventional chaintransfer agents for low Mw oligomer(s). As discussed above, low PDifavours low viscosity in the bulk and in solution (for a given Mw),which in turn leads to longer open time and wet edge time. CCTP is alsoparticularly useful for preparing a precursor vinyl oligomer(s).

Surfactants and/or high shear can be utilised in order to assist in thedispersion of the vinyl oligomer(s) in water (even if it isself-dispersible). Suitable surfactants include but are not limited toconventional anionic, cationic and/or non-ionic surfactants and mixturesthereof such as Na, K and NH₄ salts of dialkylsulphosuccinates, Na, Kand NH₄ salts of sulphated oils, Na, K and NH₄ salts of alkyl sulphonicacids, Na, K and NH₄ alkyl sulphates, alkali metal salts of sulphonicacids; fatty alcohols, ethoxylated fatty acids and/or fatty amides, andNa, K and NH₄ salts of fatty acids such as Na stearate and Na oleate.Other anionic surfactants include alkyl or (alk)aryl groups linked tosulphonic acid groups, sulphuric acid half ester groups (linked in turnto polyglycol ether groups), phosphonic acid groups, phosphoric acidanalogues and phosphates or carboxylic acid groups. Cationic surfactantsinclude alkyl or (alk)aryl groups linked to quaternary ammonium saltgroups. Non-ionic surfactants include polyglycol ether compounds andpreferably polyethylene oxide compounds as disclosed in “non-ionicsurfactants—Physical chemistry”, edited by M J Schick, M. Decker 1987.The amount of surfactant used is preferably 0 to 15% by weight, morepreferably 0 to 8% by weight, still more preferably 0 to 5% by weight,especially 0.1 to 3% by weight and most especially 0.3 to 2% by weightbased on the weight of the crosslinkable vinyl oligomer(s).

The aqueous composition of the invention may optionally but preferablyinclude a polymer(s) dispersed therein which is not a crosslinkablevinyl oligomer (or a non-vinyl oligomer whether crosslinkable ornon-crosslinkable) and preferably has an Mw≧90,000 Daltons, hereintermed a “dispersed polymer” for convenience. Preferably the weightaverage molecular weight of the dispersed polymer(s) in the aqueouspolymer dispersion is in the range of from 100,000 to 6,000,000, morepreferably in the range of from 150,000 to 2,000,000, and especially inthe range of from 250,000 to 1,500,000 Daltons. If the dispersedpolymer(s) is fully precrosslinked its Mw will be infinite. The Mw ofthe dispersed polymer(s) may be <90,000 Daltons, with the proviso thatthe solution viscosity of the dispersed polymer(s) is >150 Pa·s asdetermined from a 80% by weight solids solution of the dispersedpolymer(s) in at least one of the solvents selected from the groupconsisting of N-methylpyrrolidone, n-butyl glycol and mixtures thereof,using a shear rate of 90±5 s⁻¹ and at 50±2° C.

Preferably, the solution viscosity (if measurable) of the dispersedpolymer(s) when used in the aqueous composition of the invention is ≧250Pa·s, more preferably ≧500 Pa·s, and especially ≧1000 Pa·s as determinedfrom a 80% by weight solids solution of the dispersed polymer(s) in atleast one of the solvents, selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof at a shear rateof 90±5 s⁻¹ and at 50±2° C.

The solution viscosity of the dispersed polymer(s) may not be measurableif for example the weight average molecular is so high as to render thedispersed polymer(s) insoluble in organic solvents or if the dispersedpolymer(s) is fully or partially cross linked, again rendering itinsoluble.

The dispersed polymer(s) may be film forming or non-film forming atambient temperature; preferably the dispersed polymer(s) is non-filmforming at ambient temperature. Preferably the aqueous composition ofthe invention does include such a dispersed polymer(s).

The crosslinkable vinyl oligomer(s) can thus be (and preferably is)combined with a dispersed polymer(s) to further improve the provision ofa binder system for providing an aqueous composition with the desiredbalance of long open/wet edge time and a reduced tack free time.

The presence of the crosslinkable vinyl oligomer(s) (as discussed above)provides the defined long open time and wet edge time, whilst thepresence of the dispersed polymer(s) (e.g. in the form of a polymerlatex) appears to assist in reducing the drying time of the composition,even though its presence may not always be essential to achieve thebroadest scope of defined requirements in this respect.

Accordingly in a further, and preferred, embodiment of the presentinvention there is provided an aqueous coating composition as definedherein additionally comprising a dispersed polymer(s).

The dispersed polymer(s) may for example be the product of an aqueousemulsion polymerisation or a preformed polymer dispersed in water.

Preferably the dispersed polymer(s) has a measured Tg using differentialscanning calorimentry (DSC) which is in the range of from −50 to 300°C., more preferably in the range of from 0 to 250° C., most preferablyin the range of from 25 to 200° C. and especially in the range of from35 to 125° C. If the dispersed polymer(s) is a vinyl polymer, the vinylpolymer may be a sequential polymer, i.e. the vinyl polymer will havemore than one Tg. Especially preferred is a vinyl polymer with 10 to 50wt. % of a soft part with a Tg in the range of from −30 to 20° C. and 50to 90 wt. % of a hard part of with a Tg in the range of from 60 to 110°C. This combination provides an additional advantage of improved blockresistance of the resultant coating, especially when co-solvent levelsof 0 to 15 wt. %, more preferably 0 to 5 wt. % and most preferably 0 to3 wt. %. of the aqueous composition are used. A simple blend of high andlow Tg dispersed polymers can also be used to achieve the same orsimilar advantage. Blocking is the well-known phenomenon of coatedsubstrates which are in contact tending to unacceptably adhere to eachother, such as windows and doors in their respective frames,particularly when under pressure, as for example in stacked panels.

Preferably the dispersed polymer(s) has an average particle size in therange of from 25 to 1000 nm, more preferably 60 to 700 nm, morepreferably 100 to 600 nm and especially in the range of from 175 to 500nm. The dispersed polymer may also have a polymodal particle sizedistribution.

The dispersed polymer(s) preferably has a low solubility, measurable bythe centrifuge test as described herein, in the aqueous medium of thecomposition of the invention. However some of the dispersed polymer(s)may be soluble. Preferably at least 30%, more preferably at least 60%,most preferably at least 90% of the dispersed polymer(s) is present asinsoluble polymer over the whole pH range.

The dispersed polymer(s) may for example be one or more of vinylpolymer, polyurethane, polyester, polyether, polyamide, and polyepoxide.The dispersed polymer(s) may also be a hybrid of two or more differentpolymer types such as urethane-acrylic polymers (as described in forexample U.S. Pat. No. 5,137,961), epoxy-acrylic polymers andpolyester-acrylic polymers. The dispersed polymer(s) may also be anorganic-inorganic hybrid, for example silica particles grafted with avinyl polymer(s). Blends of dispersed polymers may of course also beused.

The dispersed polymer(s) optionally contains acid groups. The preferredacid value of the dispersed polymer(s) depends on the type and molecularweight of crosslinkable vinyl oligomer and (if present) the type ofcosolvent used. If the crosslinkable vinyl oligomer is hydrophilic, thecosolvent (if used) is preferably also of a hydrophilic nature and thusa low acid value of the dispersed polymer(s) is preferred (preferablybelow 60, more preferably below 40, still more preferably below 30,especially below 24, more especially below 19 and most especiallypreferably below 15 mg KOH/g). If however a hydrophobic crosslinkablevinyl oligomer is used, for instance based on (at least partly)unsaturated fatty acid and without dispersing groups, the cosolvent ispreferentially of a hydrophobic nature (if at all present) and thereforemuch higher acid values (up to an acid value of 160, most preferably upto an acid value of 125, most preferably up to an acid value of 100 mgKOH/g) of the dispersed polymer(s) may be tolerated to give the desiredproperties.

In a special embodiment, 0 to 15 wt. % of a co-solvent (based on totalbinder solids where the binder includes the crosslinkable oligomer(s),non-crosslinkable oligomer(s) and any dispersed polymer(s)) is used,where the dispersed polymer(s) has an acid value below 20 mgKOH/g andthe crosslinkable vinyl oligomer(s) is present in an amount (based ontotal binder solids) of 35 to 65 wt. %, and the crosslinkable vinyloligomer(s) comprising 45 to 70 wt. % of fatty acid groups.

The dispersed polymer(s) may optionally contain hydroxyl groups. If thedispersed polymer(s) is a vinyl polymer comprising polymerised(meth)acrylic monomers then preferably the hydroxyl group content in thevinyl polymer is below 1.0 wt. %, more preferably below 0.5 wt. % andmost preferably below 0.2 wt. % based on the weight of the vinylpolymer.

The dispersed polymer(s) may optionally contain amide groups (suchgroups being for example obtainable from amide functional monomers suchas (meth)acrylamide). If the dispersed polymer(s) is a vinyl polymer(s)comprising (meth)acrylamide monomers, then preferably the amide groupcontent in the vinyl polymer is below 3.0 wt. %, more preferably below1.5 wt. % and most preferably below 0.6 wt. % based on the weight of thevinyl polymer(s).

The dispersed polymer(s) may optionally contain wet-adhesion promotinggroups such as acetoacetoxy groups, (optionally substituted) amine orurea groups, for example cyclic ureido groups, imidazole groups,pyridine groups, hydrazide or semicarbazide groups.

The dispersed polymer(s) may optionally be crosslinkable, for examplethe dispersed polymer(s) may contain crosslinker groups which allowindependent crosslinking of the dispersed polymer(s) and/or allowparticipation in the crosslinking reaction of the crosslinkable vinyloligomer(s), thus speeding up the drying rate and improving theproperties of the final coating (e.g. chemical resistance and scratchresistance). Examples of such crosslinker groups include groups whichcan take part in the autoxidation and groups which will effectcrosslinking other than by autoxidation, for example by Schiff base andsilane condensation reactions as discussed above for crosslinkable vinyloligomer(s).

In a preferred embodiment the dispersed polymer(s) contains crosslinkergroups which can participate in the preferred autoxidative crosslinkingreactions of an autoxidisably crosslinkable vinyl oligomer(s).

In a preferred embodiment the dispersed polymer(s) may be fully orpartially pre-crosslinked (i.e. fully or partially crosslinked whilepresent in the invention coating composition and prior to coating). Ifthe dispersed polymer(s) is a vinyl polymer pre-crosslinking may beachieved by using polyunsaturated monomers during the vinyl polymersynthesis such as allyl methacrylate, diallyl phthalate, tripropyleneglycol di(meth)acrylate, 1,4-butanediol diacrylate, trimethylol propanetriacrylate, (2-dicyclopentenyloxy)ethyl (meth)acrylate anddicyclopentadiene (meth)acrylate. Allyl methacrylate is most preferred.Alternatively very low levels of initiator may be used, leading tochain-transfer to the vinyl polymer and hence to grafting and high Mw.Other ways to generate pre-crosslinking in a vinyl polymer is to includethe use of monomer(s) bearing groups which may react with each otherduring synthesis to effect pre-crosslinking, for exampleglycidylmethacrylate and acrylic acid, n-methylol (meth)acrylamide,n-butylol (meth)acrylate and isobutylol (meth)acrylamide.

If the dispersed polymer(s) is a dispersed vinyl polymer(s), the vinylpolymer(s) may be prepared from for example the vinyl monomer(s)described herein for the preparation of the vinyl oligomer(s).

If the dispersed polymer(s) is a dispersed vinyl polymer, then thedispersed vinyl polymer may in some embodiments comprise at least 15 wt.%, more preferably at least 40 wt. % and most preferably at least 60 wt.% of polymerised vinyl acetate. If the vinyl polymer comprises at least50 wt. % of polymerised vinylacetate then preferably the vinyl polymeralso comprises 10–49 wt. % of either n-butylacrylate or a branchedvinylester, for example Veova 10.

In preferred embodiment the dispersed vinyl polymer comprises:

-   -   I 15 to 60 wt. % of styrene and/or α-methylstyrene;    -   II 15 to 80 wt. % of one or more of methyl methacrylate, ethyl        methacrylate, cyclohexyl(meth)acrylate, and n-butyl        methacrylate;    -   III 0 to 5 wt. % more preferably 0 to 3.5 wt. % of a vinyl        monomer containing carboxylic acid groups;    -   IV 0 to 10 wt. %, more preferably 0 to 5 wt. % of vinyl        monomer(s) containing a non-ionic water-dispersing group(s);    -   V 5 to 40 wt. % of vinyl monomer(s) other than as in I to IV, VI        and VII;    -   VI 0 to 5 wt. % of vinyl monomer(s) containing a wet-adhesion        promoting group(s) or a crosslinker group(s) (excluding any        within the scope of III and VII); and    -   VII 0 to 8 wt. %, more preferably 0 to 4 wt. %, and most        preferably 0.5 to 3 wt. % of polyethylenically unsaturated vinyl        monomer(s),        wherein I)+II) add up to at least 50 wt. % and        I+II+III+IV+V+VI+VII add up to 100 wt. %.

The dispersed polymer(s) can be prepared by any known technique.Preparation techniques particularly include either dispersing apre-formed polymer or polymer solution is in water or if the polymer isa vinyl polymer directly synthesising the vinyl polymer in water (forexample by emulsion polymerisation, micro-suspension polymerisation ormini emulsion polymerisation). Methods for preparing aqueous dispersedpolymer(s) are reviewed in the Journal of Coating Technology, volume 66,number 839, pages 89–105 (1995) and these methods are included herein byreference. Preferably dispersed vinyl polymer(s) are prepared by theemulsion polymerisation of free radically polymerisable olefinicallyunsaturated monomers (Emulsion Polymerisation and Emulsion Polymers, P.Lovell, M. S. El-Aasser, John Wiley, 1997). Any published variant of theemulsion polymerisation process may be utilised to prepare the dispersedpolymer(s), including the use of seeded emulsion polymerisationtechniques to control particle size and particle size distribution,especially when working in the particle size range 300–700 nm when theseeded technique is useful for giving good particle size control. Otheruseful techniques are the so called sequential polymerisation techniqueand the power feed technique (chapter 23 in “Emulsion Polymers andEmulsion Polymerisation” D R Basset and A E Hamielec, ACS SymposiumSeries No 165, 1981). Suitable free radically polymerisable olefinicallyunsaturated monomers include those described above for the preparationof vinyl oligomer(s) and any others that may be useful for preparing thedispersed polymer(s) with characteristics as described above.

Preferably the dispersed polymer(s) is colloid stable and it is alsodesirable that colloid stability is maintained for as long as possibleinto the drying process since early loss of colloid stability can bringa premature end to open time. Since the final coating composition mayoften contain co-solvents and dissolved ionic species (e.g. from pigmentdissolution and from the presence of neutralising agents), it isdesirable that the colloid stability of the aqueous dispersed polymer(s)is adequate to withstand any destabilising influences of thesecomponents. Colloid stability may be achieved by the addition ofconventional non-ionic surfactants, optionally with the addition ofanionic surfactants at any stage during the preparation of the aqueouscomposition of the invention. Strongly adsorbing surfactants capable ofproviding steric stability are preferred. Higher levels of colloidstability may be obtained by chemically binding or partially bindinghydrophilic stabilising groups such as polyethylene oxide groups to thesurface of dispersed polymer(s) particles. Suitable surfactants andstabilising groups are described in “Non Ionic Surfactants-PhysicalChemistry” (M J Schick, M Dekker Inc. 1987) and “Polymer Colloids”(Buscall, Corner & Stageman, Elsevier Applied Science Publishers 1985).

Chemical binding (grafting) of hydrophilic stabilising groups ontodispersed polymer(s) particles can be achieved by the use of acomonomer, polymerisation initiator and/or chain transfer agent bearingthe stabilising group, for example methoxy(polyethylene oxide)₃₀methacrylate may be introduced as a comonomer into an emulsionpolymerisation to give rise to stabilised dispersed polymer particleswith bound polyethylene oxide groups on the particle surface. Anothermethod of producing a strongly sterically stabilised dispersedpolymer(s) is to introduce cellulosic derivatives (e.g. hydroxy ethylcellulose) during an emulsion polymerisation (see for example D H Craig,Journal of Coatings Technology 61, no. 779, 48, 1989). Hydrophilicstabilising groups may also be introduced into a preformed polymerbefore it is subsequently dispersed in water, as described in EP 0317258where polyethylene oxide groups are reacted into a polyurethane polymerwhich is subsequently dispersed in water and then chain extended.

The combination of crosslinkable vinyl oligomer(s) (and othercrosslinkable or non-crosslinkable oligomers, if used) and dispersedpolymer(s) is most conveniently prepared by physically blending thecorresponding aqueous dispersions. However other methods of preparingthe combination can sometimes be utilised. One such method is to preparethe crosslinkable vinyl oligomer(s) in organic solvent solution aspreviously discussed, and to disperse this vinyl oligomer(s) solutiondirectly into an aqueous dispersed polymer(s). Alternatively the organicsolvent can be removed from the crosslinkable vinyl oligomer(s)solution, and the dry vinyl oligomer(s) directly dispersed into anaqueous dispersed polymer(s). Another method is to introduce thecrosslinkable vinyl oligomer(s) into an aqueous emulsion polymerisationreaction which produces the dispersed polymer(s). Such an introductionof crosslinkable vinyl oligomer(s) can either be at the commencement ofthe emulsion polymerisation or during the emulsion polymerisation. Thecrosslinkable vinyl oligomer(s) may also be diluted with reactivediluent (for example vinyl monomers) at any stage of its preparation andthen dispersed into a dispersed polymer(s), followed by polymerisationor partial polymerisation of the reactive diluent in the presence of theaqueous vinyl oligomer(s) and the optional dispersed polymer(s).Optionally, depending on the nature of the reactive diluent, no furtherpolymerisation of the reactive diluent prior to use in a coating may berequired.

Alternatively the crosslinkable vinyl oligomer(s) and dispersedpolymer(s) may be combined by preparing a redispersible dry powder formof the dispersed polymer(s), and then dispersing the redispersible drypowder directly into an aqueous dispersion of the crosslinkable vinyloligomer(s). Methods for preparing redispersible dry powders frompolymer emulsions are described for example in U.S. Pat. No. 5,962,554,DE 3323804 and EP 0398576.

Preferably the aqueous composition of the invention gives clear films onfilm formation after coating the aqueous composition onto a substrate.It may be that if there is some incompatibility between the vinyloligomer(s) and the dispersed polymer(s) then one of them may coagulateon film formation resulting in a haze in the film, which may not bedesirable for some applications.

Preferably the ratios by weight of solid material of crosslinkable vinyloligomer(s) (and other crosslinkable or non-crosslinkable oligomers ifused) to the dispersed polymer(s) is in the range of from 100:0 to10:90, more preferably in the range of from 90:10 to 20:80, still morepreferably in the range of from 80:20 to 30:70, and especially in therange of from 65:35 to 35:65.

The aqueous coating compositions of the invention are particularlyuseful when in the form of final coating formulations (i.e. compositionintended for application to a substrate without any further treatment oradditions thereto) such as protective, adhesive or decorative coatingcompositions (for example paint, lacquer or varnish) wherein aninitially prepared composition may be optionally further diluted withwater and/or organic solvents and/or combined with further ingredients,or may be in more concentrated form by optional evaporation of waterand/or organic components of the liquid medium of an initially preparedcomposition. The invention composition can contain co-solvent or amixture of co-solvents. Preferably the invention composition contains≦18% by weight of co-solvent(s), more preferably ≦10%, more preferably≦5%, especially ≦3%, and most especially 0% by weight based on theinvention composition.

Preferably the evaporation rate of the co-solvent is ≦0.6, morepreferably ≦0.15, most preferably ≦0.08 and especially ≦0.035. Valuesfor evaporation rates were published by Texaco Chemical Company in abulletin Solvent Data; Solvent Properties (1990). These values arerelative to the evaporation rate of n-butylacetate for which theevaporation rate is defined as 1.00. Determination of evaporation ratesof solvents not listed in this bulletin is as described in ASTM D3539.

In a special embodiment, the amount of co-solvent(s) used in theinvention composition is preferably linked to the Mw of thecrosslinkable vinyl oligomer(s) in the composition. For vinyloligomer(s) with Mw in the range 1,000 to 40,000 Daltons, the amount ofco-solvent is preferably 0 to 15 wt. % based on the weight of thecomposition, more preferably 0 to 10 wt %. For oligomers with Mw in therange >40,000 to 80,000 Daltons, the corresponding figures for thepreferred amount of co-solvent are 0 to 25 wt. %, more preferably 5 to20 wt. %.

Furthermore, there is also a preferred relationship between the amountof co-solvent used and the amount of binder solids (vinyl oligomer(s)plus optional dispersed polymer(s)), viz the amount of co-solvent ispreferably ≦50 wt. % based on the weight of binder polymer solids in thecomposition, more preferably ≦35 wt. %, more preferably ≦20 wt. %, morepreferably ≦10 wt. %, and especially preferably 0 wt. %.

An advantage of the present invention is that co-solvent can, if as isoften required for environmental and safety reasons, be present at avery low concentrations because of the plasticising nature of thecrosslinkable vinyl oligomer(s). Preferably the co-solvent(s) to waterratio is below 1.0, more preferably below 0.5, more preferably below 0.3and especially below 0.15. The co-solvent(s) can all be added at thefinal formulation step. Alternatively some or all of the co-solvent inthe final formulation can be the cosolvent utilised in a solutionpolymerisation to prepare the crosslinkable vinyl oligomer(s) (or itsprecursor oligomer(s)). An important consideration when choosing aco-solvent is whether or not it is compatible with the crosslinkablevinyl oligomer(s) and/or the dispersed polymer(s) and the effect of anyco-solvent partitioning (and the partitioning of the co-solvent in the(aqueous) oligomer phase versus the dispersed polymer particles ispreferably >1/1, more preferably >2/1 and most preferably >3/1). If theco-solvent is more compatible with the dispersed polymer it will swellthe polymer, thus increasing the overall viscosity. Preferably anyco-solvent present in the aqueous composition of the invention is morecompatible with the vinyl oligomer(s) than with the dispersedpolymer(s), so that the dispersed polymer(s) undergoes little if anyswelling by the co-solvent. The co-solvent selection is often determinedby experimentation and/or by the use of a solubility parameter concepti.e. maximising the difference in the solubility parameter of thedispersed polymer(s) and solvent leads to a minimisation of theco-solvent uptake by the dispersed polymer(s). Solubility parameters ofa range of solvents and a group contribution method for assessing thesolubility parameters of polymers are given by E A Grulke in the“Polymer Handbook” (John Wiley pages 519–559,1989) and by D W VanKrevelen and P J Hoftyzer in “Properties of Polymers. Correlations WithChemical Structure” (Elsevier, N.Y., 1972 chapters 6 and 8). Co-solventuptake of the dispersed polymer(s) may also be decreased by increasingits Tg so that the dispersed polymer(s) is in the glassy region atambient temperature, or by pre-crosslinking the dispersed polymer(s) asdescribed above. Other ways of introducing pre-cross linking intodispersed polymer(s) are known in the art, for example U.S. Pat. No.5,169,895 describes the preparation of pre-crosslinked polyurethaneaqueous dispersions by the use of tri-functional isocyanates in thesynthesis.

Optionally external crosslinking agent(s) may be added to the aqueouscomposition of the invention to aid crosslinking during or after drying.Examples of reactive functional groups which may be utilised forexternal crosslinking agent(s) include but are not limited to hydroxylfunctional groups reacting with isocyanate (optionally blocked),melamine or glycouril functional groups; keto, aldehyde and/oracetoacetoxy carbonyl functional groups reacting with amine or hydrazinefunctional groups; carboxyl functional groups reacting with aziridine,epoxy or carbodiimide functional groups; silane functional groupsreacting with silane functional groups; epoxy functional groups reactingwith amine or mercaptane groups as well as carboxyl functional groupsundergoing metal ion (such as zinc) crosslinking.

A known problem with many autoxidisable coating compositions is that theresultant coatings have a tendency to yellow, in particular where theautoxidisable groups are derived from polyunsaturated fatty acids, suchas for example tung oil fatty acid, linolenic acid, eleostearic acid,arachidonic acid, clupanadonic acid, and fatty acids obtainable fromdehydrated castor oil. This may be unacceptable depending on the desiredcolour of the resultant coating. Preferably the aqueous composition hasa starting yellowness value of less than 10, more preferably less than 7and most preferably less than 4, measured as described herein.Preferably the aqueous composition has an increase in yellowing indarkness of less than 7, more preferably less than 5, most preferablyless than 3 and preferably the aqueous composition has an increase inyellowing in daylight of less than 4, more preferably less than 3 andmost preferably less than 2 as measured by the test method describedherein. Furthermore, the absolute yellowness (i.e. yellowness at startplus yellowness due to ageing) of the aqueous composition is preferablyless than 12, more preferably less than 10, still more preferably lessthen 8, and most preferably less than 6.

In a further embodiment of the present invention there is provided anaqueous coating composition as defined herein comprising:

i) 3 to 26% of a crosslinkable oligomer(s) by weight of the compositionof which at least 52 wt % is a crosslinkable water-dispersible vinyloligomer(s);

ii) 0 to 6.5% of a non-crosslinkable oligomer(s) by weight of thecomposition;

iii) 10 to 56% of dispersed polymer(s) by weight of the composition;

iv) 0 to 15% of co-solvent by weight of the composition;

v) 5 to 65% of water by weight of the composition;

where i)+ii)+iii)+iv)+v)=100%.

In another embodiment of the present invention there is provided anaqueous coating composition as defined herein comprising:

i) 15 to 40% of a crosslinkable oligomer(s) by weight of crosslinkableoligomer(s), non-crosslinkable oligomer(s) and dispersed polymer(s) ofwhich at least 52 wt % is a crosslinkable water-dispersible vinyloligomer(s);

ii) 0 to 10% of a non-crosslinkable oligomer(s) by weight ofcrosslinkable oligomer(s), non-crosslinkable oligomer(s) and dispersedpolymer(s);

iii) 50 to 85% of dispersed polymer(s) by weight of crosslinkableoligomer(s), non-crosslinkable oligomer(s) and dispersed polymer(s);

where i)+ii)+iii)=100%.

The aqueous coating composition of the invention may be applied to avariety of substrates including wood, board, metals, stone, concrete,glass, cloth, leather, paper, plastics, foam and the like, by anyconventional method including brushing, dipping, flow coating, spraying,and the like. They are, however, particularly useful for providingcoatings such as decorative paints on wood and board substrates. Theaqueous carrier medium is removed by natural drying or accelerateddrying (by applying heat) to form a coating.

Accordingly, in a further embodiment of the invention there is provideda coating obtainable from an aqueous coating composition of the presentinvention.

The aqueous coating composition of the invention may containconventional ingredients, some of which have been mentioned above;examples include pigments, dyes, emulsifiers, surfactants, plasticisers,thickeners, heat stabilisers, levelling agents, anti-cratering agents,fillers, sedimentation inhibitors, UV absorbers, antioxidants,dispersants, flow agents, adhesion promoters, crosslinking agents,de-foamers, co-solvents, wetting agents and the like introduced at anystage of the production process or subsequently. It is possible toinclude an amount of antimony oxide in the dispersions to enhance thefire retardant properties.

In particular, the aqueous coating compositions of the invention (ifautoxidisable) and formulations containing them advantageously include adrier salt(s). Drier salts are well known to the art for furtherimproving curing in unsaturated film-forming substances. Generallyspeaking, drier salts are metallic soaps, that is salts of metals andlong chain carboxylic acids. It is thought that the metallic ions effectthe curing action in the film coating and the fatty acid componentsconfer compatibility in the coating medium. Examples of drier metals arecobalt, manganese, zirconium, lead, neodymium, lanthanum and calcium.The level of drier salt(s) in the composition is typically that toprovide an amount of metal(s) within the range of from 0.01 to 0.5% byweight based on the weight of autoxidisable vinyl oligomer(s) andautoxidisable dispersed polymer(s).

Drier salts are conventionally supplied as solutions in white spirit foruse in solvent-borne alkyd systems. They may, however, be used quitesatisfactorily in aqueous coating compositions since they can normallybe dispersed in such systems fairly easily. The drier salt(s) may beincorporated into the aqueous coating composition at any convenientstage. For example the drier salt(s) may be added prior to dispersioninto water. Drier accelerators may be added to the drier salts. Suitabledrier accelerators include 2,2′-bipyridyl and 1,10-phenanthroline.

If desired the aqueous coating composition of the invention can be usedin combination with other polymer dispersions or solutions which are notaccording to the invention.

The solids content of the aqueous coating composition of the inventionis preferably ≧15 wt %, more preferable ≧25 wt %, still more preferably≧35 wt %, especially ≧40 wt % more especially ≧45 wt % and mostespecially ≧50 wt %. The upper limit of solids content is usually notmore than 90 wt %, more preferably not more then 80 wt %.

FIG. 1 to 4 illustrate the drying profile of a composition according tothe present invention [Example 10], where the equilibrium viscosity ismeasured as the solids content increases.

FIG. 1 shows the drying profile measured using a shear rate of 0.0997s⁻¹.

FIG. 2 shows the drying profile measured using a shear rate of 0.990s⁻¹.

FIG. 3 shows the drying profile measured using a shear rate of 9.97 s⁻¹.

FIG. 4 shows the drying profile measured using a shear rate of 78.6 s⁻¹.

The present invention is now illustrated by reference to the followingexamples. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis. The term “working” means that the exampleaccording to the invention. The term “non-working” means that it is notaccording to the invention (i.e. comparative).

Test Methods:

To test for the open time and wet edge time of the aqueous compositionsprepared as described in the Examples below, the aqueous composition wasapplied using a wire rod to a test chart (18×24 cm, form 8B—display,available from Leneta Company) at a wet film thickness of 120 μm. Opentime and wet edge time tests were performed at fairly regular timeintervals according to the approximate expected final times in each case(being determined roughly from a trial run) the intervals betweenmeasurements decreasing towards the end of the run. The measurementswere carried out at relative humidity levels of 50+/−5%, temperatures of23+/−2° C. and an air flow of ≦0.1 m/s.

Open Time:

The open time was determined by brushing at regular intervals (asmentioned above) a virgin 75 cm² area of the coated chart with a brush(Monoblock no 12, pure bristles/polyester 5408–12) carrying some more ofthe composition with a brush pressure of 100–150 g during 30 seconds. Inthis time the brush was moved in one set comprising 5 times in thedirection of the width of the substrate and 5 times in the direction oflength of the substrate before the homogeneity of the coating wasvisually assessed. Once the composition carried on the brush no longerformed a homogeneous layer with the coating on the substrate the opentime was considered to be over.

Wet Edge Time:

The wet edge time was determined by brushing at regular time intervals(as mentioned above) a virgin 25 cm² edge area of the coated chart witha brush (Monoblock no 12, pure bristles/polyester 5408–12) carrying somemore of the composition with a brush pressure of 100–150 g during 30seconds. In this time the brush was moved in one set comprising 5 timesin the direction of the width of the substrate and 5 times in thedirection of length of the substrate before the homogeneity of thecoating was visually assessed. Once the composition carried on the brushno longer formed a homogeneous layer with the coating on the substrateand/or a visible lap line could be seen the wet edge time was consideredto be over.

Drying Time:

To test the dust-free, tack-free and thumb-hard drying stages of theaqueous compositions prepared in the Examples described below, thecomposition was applied to a glass plate at a wet film thickness of 80μm, which corresponded to a dry film thickness of about 30 μm. Dryingtime tests were performed at regular time intervals at relative humiditylevels of 50+/−5%, temperatures of 23+/−2° C. and an air flow ≦0.1 m/s.

Dust-Free Time:

The dust-free time was determined by dropping a piece of cotton wool(about 1 cm³, 0.1 g) onto the drying film from a distance of 25 cm. Ifthe piece of cotton wool could immediately be blown from the substrateby a person without leaving any wool or marks in/on the film, the filmwas considered to be dust-free.

Tack-Free Time:

The tack-free time was determined by placing a piece of cotton wool(about 1 cm³, 0.1 g) on the drying film and placing a metal plate (witha diameter of 2 cm) and then a weight of 1 kg onto the piece of cottonwool (for 10 seconds). If the piece of cotton wool could be removed fromthe substrate by hand without leaving any wool or marks in or on thefilm, the film was considered to be tack-free.

Thumb-Hard Time:

The thumb-hard was determined by placing the coated glass plate on abalance and a thumb was pressed on the substrate with a pressure of 7kg. The thumb was then rotated 90° under this pressure. If the film wasnot damaged the coating was dried down to the substrate level andconsidered to be thumb-hard.

Viscosity Measurements:

All viscosity measurements were performed on a Bohlin Rheometer VOR or aTA Instruments AR1000N Rheometer, using the cup & spindle (C14), cone &plate (CP 5/30) and/or plate & plate (PP15) geometry, depending on theviscosity of the sample to be measured.

Solution Viscosity

For the solution viscosity measurements (both at 50±2° C. and at 23±2°C.), the cone & plate (CP 5/30) geometry was used and the measurementswere performed at a shear rate of 92.5 s⁻¹. If the oligomer solutionswere too low in viscosity to remain in between the cone and the plate,the Cup & Spindle C14 geometry was used and the viscosity measurementswere performed at a shear rate of 91.9 s⁻¹. For both geometries, the gapbetween the Cone and the Plate (or between the Cup and the Spindle) wasset to 0.1 mm, prior to each measurement. The solution viscosities ofthe oligomers were measured using the solvent systems and the conditionsas defined herein in the statements of invention:

-   1. The 80% solids solution: The oligomer was diluted (if necessary)    with the appropriate solvent to an 80% solids solution (in NMP, BG    or a mixture of NMP and BG at any ratio) which was homogenised by    stirring the solution for 15 minutes at 50±2° C.-   2. The 70% solids solution: The oligomer was diluted with the    appropriate solvent (or mixture of solvents) to result in a 70%    solids solution (either in NMP/water/DMEA or in BG/water/DMEA, or in    (a mixture of NMP and BG at any ratio)/water/DMEA; in both solvent    mixtures the solvents should be present in a weight ratio of    20/17/3, respectively) which was homogenised by stirring the    solution for 15 minutes at 50° C. The resulting solution was    subsequently cooled prior to the viscosity measurement at 23±2° C.-   3. A sample of oligomer solution was placed in the appropriate    measurement geometry (Cone & Plate CP 5/30 or Cup & Spindle C14    geometry). The solution viscosity of the oligomer was measured at a    temperature of 50±2° C. for the 80% solids oligomer solution, and at    ambient temperature for the 70% solids oligomer solution. A    heating/cooling unit in the measurement geometry was used to control    the temperatures.    Equilibrium Viscosity

The equilibrium viscosity measurements were performed with the plate &plate geometry, with a 15 mm (P15) top-plate and a 30 mm (P30)bottom-plate. The gap between the two plates was set to 1.0 mm. Allcompositions were used at the solids level at which they were preparedand not diluted to lower solids levels.

Step 1: Three test charts were provided with coatings of identical filmthickness. The coatings were applied with a 120 μm wire rod and theactual film thickness (and its uniformity) was checked with a wet filmgauge, 20–370 μm, of Braive Instruments. The charts were dried underidentical conditions in an environment where the airflow was <0.1 m/s.

Step 2: One test chart was used to determine the solids increase intime. The weight of the film was monitored in time, starting right afterapplication of the film. After calculating the solids content at everymeasurement, a solids-time curve could be constructed and a trend linewas calculated for the solids of the film as a function of the dryingtime.

Step 3: The other two test charts were used to determine the equilibriumviscosity in time: approximately every 5 minutes a sample was scrapedfrom one test chart (in random order) and the viscosity of this samplewas measured at 23° C. at representative shear rates of 0.0997 s⁻¹,0.990 s⁻¹, 9.97 s⁻¹ and 78.6 s⁻¹. The measurements were continued for 90minutes, unless reproducible sampling from the test charts could not beperformed properly within that period of time (due to for example dryingof the film to reach the dust free time).

Step 4: The final drying curve of the coating as shown in FIGS. 1 to 4(in which the equilibrium viscosity is represented as a function of thesolids of the drying film) could be constructed from the solids-timecurve (Step 2) and the equilibrium viscosity data (Step 3). If theequilibrium viscosity at a shear rate of 9.97 s⁻¹ is lower than theequilibrium viscosity at a shear rate of 0.99 s⁻¹, which in turn islower than the equilibrium viscosity at a shear rate of 0.0997 s⁻¹, thecomposition may be regarded as shear thinning. If this was the case theequilibrium viscosity at 78.6 s⁻¹ was not always measured as it wouldinherently always be lower than the equilibrium viscosity at a shearrate of 9.97 s⁻¹.

Measurement of Yellowing:

The yellowness of a fresh coating and the increased yellowing of acoating exposed to daylight or darkness for a specified time period wasdetermined using a Tristimulus Colorimeter consisting of a data-station,a micro-colour meter, a calibration plate with a defined x, y and zvalue and a printer. The equipment was calibrated to the defined valuesof the calibration plate and then colour co-ordinates L, a and b, weremeasured. The colour co-ordinates define the brightness and colour on acolour scale, is where ‘a’ is a measure of redness (+a) or greenness(−a) and ‘b’ is a measure of yellowness (+b) or blueness (−b), (the moreyellow the coating, the higher the ‘b’ value). The co-ordinates ‘a’ and‘b’ approach zero for neutral colours (white, grays and blacks). Thehigher the values for ‘a’ and ‘b’ are, the more saturated a colour is.The lightness ‘L’ is measured on a scale from 0 (white) to 100 (black).

The daylight-yellowing is defined as the increase of the yellowness(Δb−day) of the coating during storage at 23±2° C. and in daylight for28 days. The dark yellowing is defined as the increase in the yellowness(Δb−dark) of the coating during storage at 23±2° C. and in the dark for14 days.

Molecular Weight Determinations

Gel permeation chromatography (GPC) analyses for the determination ofmolecular weights were performed on an Alliance Waters 2690 GPC with twoconsecutive PL-gel columns (type Mixed-C, I/d=300/7.5 mm) usingtetrahydrofuran (THF) as the eluent at 1 cm³/min and using an AllianceWaters 2410 refractive index detector. A set of polystyrene standards(analysed according to DIN 55672) was used to calibrate the GPC.

Samples corresponding to about 16 mg of solid material were dissolved in8 cm³ of THF, and the mixtures were stirred until the samples dissolved.The samples were left undisturbed for at least 24 hours for complete“uncoiling” and subsequently were filtered (Gelman Acrodisc 13 to 25 mmø CR PTFE; 0.45 μm) and placed on the auto-sampling unit of the GPC.

All species with a molecular weight less than 1000 Daltons are ignoredwhen calculating the Mw and PDi for the oligomers. When Daltons are usedin this application to give molecular weight data, it should beunderstood that this is not a true molecular weight, but a molecularweight measured against polystyrene standards as described above.

Water Solubility

The determination of the water solubility of crosslinkable vinyloligomers was determined as follows:

A sample of a crosslinkable vinyl oligomer was dispersed in water anddiluted with water/ammonia to 10% solids and the pH adjusted to thedesired pH, within a range of from 2 to 10, and the dispersion was thencentrifuged over 5 hours at 21000 rpm at 23±2° C. on a Sigma 3K30centrifuge (21,000 rpm corresponds to a centrifugal force of 40,000 g).The pH chosen should be the pH where the crosslinkable vinyl oligomer isexpected to be most soluble, for example often a pH of about 9 issuitable for anionic stabilised dispersions and a pH or about 2 is oftensuitable for cationic stabilised dispersions. After centrifugation asample of the supernatant liquid was taken and evaporated for 1 hour at105° C. to determine the solids content of the supernatant liquid. Thewater solubility percentage was calculated by dividing the amount ofsolids (g) of the supernatant by the total of amount of solids in thesample and multiplying by 100.Water Spot Resistance Test

A coating of the examples prepared below (100 μm thick (wet)) wasapplied onto a Leneta 9 Chart. The coating was allowed to dry for 1 hourat ambient temperature followed by 16 hours at 60° C. Then 1 cm³ ofwater was deposited onto the coating and covered with a watch glass.After 16 hours the glass was removed and the water drop was wiped offand the coating was examined for disfiguration.

Ammonia Spot Resistance Test

1 cm³ of a 12.5% ammonia solution was applied to a coating prepared asdescribed for the water spot test method. After 5 minutes the coatingwas examined for disfiguration.

Sandability

Sandability corresponds to the hardness of a coating at the point when acoating can be sanded properly. The composition prepared in the Examplesdescribed below was applied to a piece of wood at a wet film thicknessof 120 μm. The coating was abraded by hand with sandpaper (graindelicacy P150) at regular time intervals at relative humidity levels of50+/−5%, temperatures of 23+/−2° C. and an air flow ≦0.1 m/s. When therewas no significant clogging (or the coating started powdering) thecoating was considered to be sandable.

Materials & Abbreviations used: DEA = N,N-diethylethanolamine MPEG750 =methoxypolyethylene glycol (Mn approximately 750) DMPA =dimethylolpropionic acid MPEG350 = methoxy polyethylene glycol (Mnapproximately 350) NMP = N-methyl pyrrolidone TDI = toluene diisocyanateDowanol DPM = dipropylene glycol monomethyl ether DAPRO5005 = drier saltavailable from Profiltra 1,4-CHDM = 1,4-cyclohexanedimethanol VoranolP-400 = polypropyleneglycol available from DOW Chemical Dedico 5981 =dehydrated caster oil available from Uniqema DMEA = N,N-dimethyl ethanolamine DMBA = dimethylbenzylamine IPDI = isophorone diisocyanate TEA =triethylamine Nouracid LE80 = linseed oil fatty acid available from AKZONobel Fastcat 2005 = tin(II)chloride available from Elf-Atochem Atlas4809 = Alkyl phenol alkoxylate available from ATLAS Chemie AtpolE5720/20 = Fatty alcohol ethoxylate available from Uniqema AP = ammoniumpersulphate Aerosol OT-75 = Sodium dioctylsulphosuccinate available fromCytec MMA = methylmethacrylate EMA = ethylmethacrylate IBMA =isobutylmethacrylate DAAM = diacetoneacrylamide n-BA = n-butylacrylateAA = acrylic acid SLS = Sodium Lauryl Sulphate Akyposal NAF = Sodiumdodecylbenzenesulphonate available from KAO Chemicals Natrosol 250LR =Hydroxy ethyl cellulose available from Hercules Akyporox OP-250V = Octylphenol ethoxylate available from KAO Chemicals Surfactant = Phosphateester of nonyl phenol ethoxylate available from KAO Chemicals VeoVa 10 =Vinyl ester of versatic acid available from Shell Desmodur W =dicyclohexyl methane diisocyanate available from Bayer Priplast 3192 =Dimeric acid polyester polyol available from Uniqema BMA = n-butylmethacrylate t-BHPO = t-butyl hydroperoxide Fe^(III).EDTA = ferricethylene diamine tetracetic acid IAA = isoascorbic acid solution STY =Styrene 2-EHA = 2-Ethylhexylacrylate Dynasilan MEMO =3-Methacryloxypropyltrimethoxysilane available from Degussa HEMA =Hydroxyethylmethacrylate tEGDMA = Triethyleneglycoldimethacrylate OMKT =n-octyl mercaptane TAPEH = tert-amylperoxy-2-ethyl hexanoate SilquestA.174NT = γ-methacroyloxypropyl trimethoxysilane available from WitcoWater = demineralised water PW602 = transparent red iron oxide pigmentdispersion available from Johnson MattheyPreparation of Fatty Acid Functional Vinyl Oligomer V1 by CCTP

A 2L 3-necked round bottom reactor, equipped with stirrer and N2 inlet,was loaded with toluene (310.5 gram), glycidyl methacrylate (90 gram),MPEG methacrylate (60 gram), n-butyl methacrylate (100 gram), methylmethacrylate (50 gram), a Co catalyst (75 ppm) and azo-isobutyronitrile(AIBN, 3.0 gram). The reaction mixture was flushed with nitrogen and thetemperature was brought to 75° C. This temperature was maintained during3 hours after which an additional amount of AIBN (0.75 gram) was addedand the mixture was kept at 75° C. for 30 minutes after which thetemperature was raised to 95° C. for 30 minutes. To this vinyl oligomerprecursor solution Nouracid LE80 (169.40 gram) and dimethybenzylamine(DMBA; 0.60 gram) were added and the resulting yellowish mixture washeated at 140° C. under a positive nitrogen flow with no coolingapplied. The reaction was continued until the acid value reached 3.9 mgKOH/gram. The resulting vinyl oligomer V1 was at 100% solids. Vinyloligomer V1 had a Mn of 3623, Mw of 11408 and a PDi of 3.15, a watersolubility of 3.9% and the solution viscosity at 50° C. of a 80%solution in n-butylglycol, at a shear rate of 91.9s⁻¹ was 583 mPa·s andat 23° C. of a 70% solution in n-butylglycol/water/DMEA (20/7/3), at ashear rate of 91.9s⁻¹ was 290 mPa·s.

Preparation of Fatty Acid Functional Vinyl Oligomer V2

A 2L 3-necked round bottom reactor, equipped with stirrer and N₂ inlet,was loaded with toluene (310.5 gram), glycidyl methacrylate (90 gram),MPEG350 methacrylate (60 gram), n-butyl methacrylate (100 gram), methylmethacrylate (50 gram), n-octylmercaptane (OMKT, 7.5 gram) andtert-amylperoxy-2-ethylhexanoate (tAPEH, 3.0 gram). The reaction mixturewas flushed with nitrogen and the temperature was brought to 80° C. Thistemperature was maintained for 3 hours after which the temperature wasraised to 110° C. for 60 minutes. Next, to this mixture NourAcidLE80(169.40 gram) and dimethybenzylamine (DMBA; 0.60 gram) were added andthe resulting mixture was heated at 140° C. under a positive nitrogenflow. The reaction was continued until the acid value reached 5.1 mgKOH/gram. The resulting vinyl oligomer V2 was at 100% solids. Vinyloligomer V2 had a Mw of 15,801 a PDi of 2.31, a water solubility of 3.9%and the solution viscosity at 50° C. of a 80% solution in n-butylglycol,at a shear rate of 91.9s⁻¹ was 18 mPa·s and at 23° C. of a 70% solutionin n-butylglycol/water/DMEA (20/7/3), at a shear rate of 91.9s⁻¹ was 54mPa·s

The crosslinkable vinyl oligomers V3 to V8 were prepared according theabove procedure using the components listed in Table 1 below.

In addition the crosslinkable vinyl oligomer V5 was prepared by firstreacting allylamine with the GMA functional precursor oligomer at 45° C.during 8 hours after which the remaining epoxide rings were reacted withDedico 5981 at 140° C. as described for oligomer V2.

TABLE 1 Composition (g) V3 V4 V5 V6 V7 V8 GMA 90.00 0.00 35.38 90.00135.00 — type MPEG MA 550 550 — 550 550 350 MPEG MA 60.00 45.00 — 60.0075.00 30.00 MMA 60.00 — 58.96 45.00 — — BMA 60.00 — 58.96 45.00 — 190.00Silquest A-174NT — 30.00 — — — — MA — — — 60.00 — — 2-EHA — — — — —35.00 IBMA — 105.00 — — 45.00 — BA — — — — 45.00 — DAAM 10.00 — — — —45.00 EMA — 120.00 — — — — OMKT 15.00 15.00 5.90 15.00 15.00 7.50 TAPEH3.00 3.00 1.18 3.00 3.00 3.00 Toluene 318.00 318.00 125.00 318.00 318.00310.50 DMBA 0.60 — 0.10 0.60 0.90 — type fatty acid Dedico 5981 — Dedico5981 Dedico 5981 NourAcid LE80 — fatty acid 163.70 — 29.00 163.70 239.60— allyl amine — — 6.00 — — — Solution viscosity* 57 94 228 74 49 36Solution viscosity** 142 307 480 211 118 89 Mw 9892 8941 10243 1434613194 11899 PDi 4.41 2.36 4.20 2.28 1.77 2.00 water solubility (%) 2.11.7 0.1 0.2 0.9 4.9 *80% solids in NMP or BG at 91.9 s⁻¹ (mPa · s) andat 50° C. **70% solids in BG/H₂O/DMEA at 91.9 s⁻¹ (mPa · s) and at 23°C.Preparation of the Fatty Acid Functional Vinyl Oligomer Dispersion dV1

A 1L 3-necked round bottom flask, equipped with stirrer and N₂-inlet,was loaded the fatty acid functional vinyl oligomer V1 (40.0 g) in anitrogen atmosphere. Under stirring, N-methylpyrrolidone (8.0 g),Dowanol DPm (5.0 g), Dapro 5005 (0.67 g), DMEA (3 g), Atlas G5000 (1.35g) and water (56.7 g) were added. The dispersion was stirred for 30 minat ambient temperature and then stored under nitrogen. The resultingfatty acid functional vinyl oligomer dispersion had a pH of 10.3, and asolids content of 40.0%.

The fatty acid functional vinyl oligomer dispersions dV2 to dV8 wereprepared using the method described above for dV1 using the componentslisted in Table 2.

TABLE 2 Oligomer dispersion dV2 dV3 dV4 dV5 dV6 dV7 dV8 Oligomer code V2V3 V4 V5 V6 V7 V8 Oligomer amount (g) 12.5 10 20 12.5 20 3.75 12.5 NMP(g) 2.50 2.00 4.00 7.50 4.00 2.25 2.5 DPM (g) 1.56 1.25 2.50 4.68 2.501.41 1.56 Dapro 5005 (g) 0.15 0.12 0.23 0.15 0.23 0.04 0.21 DMEA (g)3.00 3.00 3.00 3.00 3.00 3.00 3.00 Water (g) 30.14 23.45 50.20 22.0250.20 4.29 30.23 Dispersion solids wt % 25.1 25.1 25.0 25.1 25.0 25.425.0 pH 10.1 10.2 10.1 10.4 10.2 10.4 10.2Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer U1,and Its Dispersion dU1Stage 1—Preparation of an Alkyd Polyol Mixture 1

A 2-L round bottom flask, equipped with a stirrer and a thermometer, wasloaded with DEA (247.56 g) and NaOMe (2.54 g). The mixture was heated to100° C. until the NaOMe was dissolved. Then sunflower oil (1248.08 g)was added giving a hazy reaction mixture. Stirring the hazy reactionmixture at 100 to 110° C. was continued until a clear reaction mixturewas obtained and a DEA-conversion of at least 85% was achieved, asdetermined by titration of residual amine functionality in the productwith aqueous HCl. A conversion of 94% was achieved. The resultingmixture was then cooled to 70° C. before adding H₃PO₄ (1.81 g) andstirring for 15 minutes. The product mixture was cooled to roomtemperature and stored under nitrogen.

Stage 2

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMPA (19.36 g), NMP (92.5 g), 1,4-CHDM(8.97 g), MPEG750 (18.87 g) and the alkyd polyol mixture 1 (260.43 g) ina nitrogen atmosphere. The reaction mixture was stirred until a clearsolution was obtained. At a maximum temperature of 25° C. TDI (99.89 g)was fed into this reaction mixture without exceeding a reactortemperature of 50° C. After the TDI-feed was complete, the reactionmixture was heated to 80° C. and stirred at this temperature for 1 hour.The resultant alkyd urethane oligomer was then cooled to about 70° C.,and diluted with Dowanol DPM (51.38 g). Subsequently DMEA (10.27 g)followed by the drying salt DAPRO5005 (5.84 g) was added and the mixturewas stirred for 15 minutes. Then water (155.43 g) was added and thetemperature was lowered to 55–60° C. The resultant predispersion wasstirred for an additional 15 minutes. Part of the resultantpredispersion (600 g), at 55–60° C., was dispersed in water (752.88 g;45–50° C.), over 60 minutes and under a nitrogen atmosphere. While thepredispersion is being dispersed, the temperature of the water phase was45–50° C. After the addition was complete, the final dispersion wasstirred for an additional 15 minutes, cooled to ambient temperature,filtered over a 200-mesh sieve and stored under nitrogen. The dispersionhad a solids content of 25 wt %, a pH of 6.9 and viscosity of 200(mPa·s).

The viscosity of a 80% solids solution of U1 in NMP (50° C., shear rate92.5s⁻¹) is 10.9 Pa·s.

The viscosity of a 70% solids solution of U1 in NMP/H₂O/DMEA (20/7/3)(23° C., shear rate 92.5 s⁻¹) is 6.6 Pa·s.

GPC analysis of U1: Mw=4917; PDi=1.94

Preparation of the Non-Crosslinkable Urethane Oligomer U2, and itsDispersion dU2

In a nitrogen atmosphere, a 1-L 3-necked round bottom flask, equippedwith a stirrer and a thermometer, was loaded with dimethylolpropanoicacid (DMPA; 48.00 g), N-methyl pyrrolidone (NMP; 240.00 g),methoxypolyethylene glycol (MPEG750; 19.20 g) and polypropylene glycol(Voranol P400, trademark from Dow Chemical; 618.64 g). At 50° C.,toluene diisocyanate (TDI; 274.16 g) was fed into this polyol mixturewhile the contents of the reactor were stirred. After the TDI-feed wascomplete, the reaction mixture was heated to 80° C. and stirred at thistemperature for 1 hour. The resultant NCO-free urethane oligomer U2 wasthen cooled to 70° C.

A portion of this urethane oligomer (949.80 g) was diluted withdipropylene glycol monomethyl ether (97.60 g) andN,N-dimethylethanolamine (DMEA; 25.51 g) at 60° C. and the resultingmixture was stirred for 15 min at this temperature. Then hot water wasadded (50° C.; 295.25 g) and the resulting predispersion was stirred foran additional 15 min at 55 to 60° C. A portion of 1100.00 g of thismixture was subsequently fed into water (919.97 g; 50° C.) in a separatereactor over a period of 60 minutes in a nitrogen atmosphere. Aftercomplete addition, the final dispersion was stirred for an additional 15minutes at 45 to 50° C., then cooled to ambient temperature, filteredand stored under nitrogen. The dispersion dU2 has a solids content of24.2%.

The viscosity of an 80% solids solution of U2 in NMP (50° C., shear rate91.1s⁻¹) is 57 Pa·s.

The viscosity of a 70% solids solution of U2 in NMP/H₂O/DMEA (20/7/3)(23° C., shear rate 91.9 s⁻¹) is 36.7 Pa·s.

GPC analysis of U2: Mw=10,251; Mn=4,476; PDi=2.29

Preparation of Dispersed Vinyl Polymer P1

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer vortex breakers and was loaded with demineralised water(652.57 g), Atpol E5720/20 (4.99 g) and Borax.10H2O (3.57 g) in anitrogen atmosphere. The mixture was heated whilst stirring to 80° C.and then a solution of AP (2.31 g) in demineralised water (16.00 g) wasadded. In a dropping funnel a pre-emulsion was prepared by stirring amixture of demineralised water (161.87 g), Atpol E5720/20 (94.85 g),Aerosol OT-75 (7.20 g), Borax.10H2O (1.07 g), MMA (534.18 g), n-BA(444.32 g) and AA (19.97 g). 5% of this pre-emulsion was added to thereactor at 80° C. over 5 minutes. The remainder was fed into the reactorover 160 minutes at 85° C. A solution of AP (0.53 g) in demineralisedwater (7.88 g) was added to the reactor during the first 15 minutes offeeding the pre-emulsified feed. Then the reactor content was kept at85° C. for 30 minutes, and then cooled to ambient temperature. The pHwas adjusted to 8 to 8.5 with 12.5% aqueous ammonia. The resultantproduct (P1) was filtered and collected.

The properties of P1 are listed in Table 4.

Preparation of a Sequential Dispersed Vinyl Polymer P2

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(990.94 g), SLS (30%, 0.55 g) and NaHCO₃, (4.44 g) in a nitrogenatmosphere. The mixture was heated whilst stirring to 80° C. and then asolution of AP (0.89 g) in demineralised water (5.00 g) was added. In adropping funnel a monomer mixture was prepared by stirring MMA (140.48g), n-BA (207.71 g) and AA (7.11 g). 10% of this mixture was added tothe reactor at 80° C. The remainder was fed into the reactor over aperiod of 40 minutes at 85° C. The content of a separate droppingfunnel, containing demineralised water (20.00 g), AP (0.36 g) and SLS30% (11.62 g) was added in the same time. The reactor content was keptat 85° C. for 30 minutes. A second monomer mixture was prepared in adropping funnel consisting MMA (464.91 g), n-BA (57.37 g) and AA (10.66g). The mixture was fed to the reactor after the 30 minutes period in 60minutes. The content of a separate dropping funnel, containingdemineralised water (30.00 g), AP (0.53 g) and SLS 30% (17.44 g) wasadded in the same time. The reactor content was kept at 85° C. for 45minutes and then cooled to ambient temperature. The pH was adjusted to 8to 8.5 with 12.5% aqueous ammonia. The resultant product P2 was filteredand collected.

The properties of P2 are listed in Table 4.

Preparation of Dispersed Vinyl Polymer P3

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(194.50 g), Akyposal NAF (3.00 g), Borax.10H2O (1.25 g), Acetic acid(0.50 g) and Natrosol 250LR (10.00 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 60° C. and then a solution of AP(0.50 g) in demineralised water (10.00 g) was added. In a droppingfunnel a pre-emulsion was prepared by stirring with demineralised water(171.71 g), Akyposal NAF (3.00), Borax.10H2O (1.25 g), Acetic acid (0.50g) and Akyporox OP-250V (14.29 g) followed by VeoVa 10 (125.00 g) andvinyl acetate (375.00 g). 10% of this mixture was added to the reactorat 60° C. The mixture was heated whilst stirring to 80° C. The remainderwas fed into the reactor over 90 minutes at 80° C. The content of aseparate dropping funnel, containing a solution of AP (1.15 g) indemineralised water (60.00 g), was added in the same time. Then thereactor content was kept at this temperature for 120 minutes and thencooled to ambient temperature. The pH was adjusted to 8 to 8.5 with12.5% aqueous ammonia. The resultant product P3 was filtered andcollected.

The properties of P3 are listed in Table 4.

Preparation of the Dispersed Urethane Acrylic Polymer P4

Stage 1: A 1-L 3-necked round bottom flask, equipped with a stirrer anda thermometer, was loaded with NMP (100.00 g), DMPA (24.00 g), DesmodurW (152.68 g) and Priplast 3192 (223.33 g) in a nitrogen atmosphere. Thereaction mixture was heated to 55° C., tin octoate (0.05) was added andthe temperature was raised to 90–95° C. The mixture was kept at thistemperature for 1 hour before adding tinoctoate (0.05) and the mixturewas kept at 90° C. for an additional hour. The NCO-concentration of themixture was found to be 4.83%. The resulting NCO terminated urethaneprepolymer (500.05 g) (from which samples of a total weight of 10.0 gwere taken for % NCO determination, leaving 490.05 g of prepolymer) wasthen cooled to 70° C., neutralised with TEA (17.75 g) diluted with BMA(196.02 g) and homogenised for 15 minutes at 65° C.

Stage 2: A 2-L 3-necked round bottom flask, equipped with a stirrer andthermometer, was loaded with a water phase consisting of water (1045.77g) and BMA (174.00 g) in a nitrogen atmosphere. A portion of theurethane prepolymer (625.00) prepared in Stage 1 (at 60–65° C.) was fedinto the reactor over 1 hour, keeping the temperature of the reactorcontents below 30° C. After the feed was complete, the mixture wasstirred for an additional 5 minutes before chain-extension by theaddition of an aqueous 64.45% hydrazine hydrate solution (N₂H₄.H₂O,11.43 g in 25.00 g H₂O). A reactor temperature of 36° C. was reached.Subsequently, a 5% aqueous initiator solution of t-BHPO (18.10 g) and a1% aqueous solution of Fe^(III).EDTA; 4.63 g) was added to the reactionmixture. The radical polymerisation was started by the addition of a 1%aqueous iAA (45.24 g) and the reaction temperature was allowed to reach56° C. before more aqueous iAA (45.24 g) was added. The reaction mixturewas homogenised for 15 minutes, then cooled to room temperature,filtered over a 200-mesh sieve and collected. The properties of P4 arelisted in Table 4.

Preparation of Dispersed Vinyl Polymer P5

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and baffles, was loaded with demineralised water (990.94 g),SLS 30% (0.55 g) and NaHCO₃ (4.44 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 80° C. and then a solution of AP(0.89 g) in demineralised water (5.00 g) was added. STY (468.54 g),2-EHA (361.69 g) and M (58.00 g) were mixed in a dropping funnel. 10% ofthis mixture was added to the reactor at 80° C. and remainder was fedinto the reactor over 100 minutes at 85° C. The content of a separatedropping funnel, containing demineralised water (50.00 g), AP (0.89 g)and SLS 30% (29.06 g) was added in the same time and the reactor contentwas kept at 85° C. for 45 minutes and then cooled to 60° C. At 60° C. aburn-up was applied by adding a solution of iAA (2.60 g) indemineralised water (49.00 g) to the reactor followed by a mixture oft-BHPO (80%,2.40 g) and demineralised water (18.00 g). After 60 minutesthe reactor content was cooled to ambient temperature. The pH wasadjusted to 8 to 8.5 with 12.5% aqueous ammonia. The product P5 wasfiltered and collected. The properties of P5 are listed in Table 4.

Preparation of Dispersed Polymers P6 to P11

The dispersed polymers P6 to P11 were prepared using the methoddescribed for P5 with the variations as listed in Table 3a. Theproperties of P6 to P11 are listed in Table 4. The Mn and Mw of P1 toP12 could not be measured.

Preparation of a Fatty Acid Functional Dispersed Polymer P12

In a 1L 3-necked round bottom reactor, equipped with stirrer and N₂inlet, Nouracid LE80 (398.8 g), GMA (201.2 g), Irganox 1010 (0.10 g),Phenothiazine (0.10 g) and benzyl trimethylammonium hydroxide (40 wt %in water; 1.05 g) were loaded. The reactor was purged with nitrogen andthe yellow reaction mixture was heated and stirred at 155° C. until theacid value had dropped to 3.7 mg KOH/g. After cooling to ambienttemperature, the product was collected and stored under nitrogen.

A portion of 161.3 g of this adduct was mixed with MAA (40.3 g) andtransferred into a dropping funnel. This mixture was slowly added over aperiod of one hour to a 1L 3-necked round bottom reactor containing asolution of lauroyl peroxide (21.4 g) in butyl glycol (273.0 g) at 125°C. in a nitrogen atmosphere. After complete addition, the resultingcopolymer solution was cooled to 50° C. and subsequently concentrated invacuo to 80% solids using a rotary evaporator. To the resulting yellowsolution, a mixture of water (580.0 g), aqueous ammonia (25%; 12.0 g)and SLS (4.4 g) was added at 70° C. A mixture of MMA (225.5 g) and BA(92.5 g) was added to the resulting dispersion and the reaction mixturewas stirred for 30 minutes at 70° C. The reaction mixture was heated to85° C. and a solution of ammonium persulphate (0.86 g) in water (20.0 g)was added over a period of 10 min. The mixture was stirred at 85° C. for3 h. Then a second portion of ammonium persulphate (0.86 g) in water(20.0 g) was added and the mixture was stirred at 85° C. for 30 minutes.Then a third portion of ammonium persulphate (0.86 g) in water (20.0 g)was added and the mixture was stirred for an additional 30 minutes at85° C. The resulting dispersion was cooled to ambient temperature,filtered and stored under nitrogen. The dispersion had a solids contentof 39.3%, a pH of 7.7 and contained 2.59% butyl glycol on totaldispersion.

TABLE 3 Components (g) P6 P7 P8 P9 P10 P11 Reactor phase Water 912.19960.66 990.94 1001.24 960.66 990.94 SLS 30% —  72.94  0.55 —  72.94 0.55 Surfactant  0.83 — — — — — NaHCO₃  4.12  4.38  4.44  4.46  4.38 4.44 Shot at 80° C. AP  0.83  0.88  0.89  0.89  0.88  0.89 Water  5.00 5.00  5.00  5.00  5.00  5.00 Monomer mixture STY — — — — — 399.70 MMA577.36 332.60 617.32 352.94 759.26 124.35 BA 236.86 402.63 253.15 521.85 89.76 133.24 BMA — — — — — 204.29 AA  16.62  17.77  17.85  17.51  17.77MAA —  87.53 — — — — Dynasilan  41.54 — — — — — MEMO HEMA —  52.52 — — —— TEGDMA — — — —  8.75 — IOTG — — — — — — AAEM — — — — — — Separate feedWater  50.00  50.00  50.00  50.00  50.00  50.00 AP  0.83  0.88  0.89 0.89  0.88  0.89 SLS 30% — —  29.06  14.88 —  29.06 Surfactant 123.79 —— — — — P11 only = Burn-up at 60° C. with IAA (0.88 g) water (12 g)tBHPO (0.88 g) and water (26.7 g)

TABLE 4 Parameter P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 Solids [wt %]51.2 45.1 50.3 35.2 42.4 44.6 21.4 45.0 45.0 44.6 44.3 39.3 pH 8.3 8.38.2 7.9 8.3 8.2 8.0 8.2 8.2 8.3 8.2 7.7 Particle size [nm] 450 230 33065 255 390 69 307 590 67 230 — Measured Tg*[° C.] 25 2 24 43 27 58 40 572 96 54 49 Acid value** 15.6 15.6 0 12.4 50.6 15.6 63.4 15.6 15.6 15.615.6 — *with DSC (midpoint) **Theoretical on solids [mgKOH/g]Preparation of Blends of the Dispersed Oligomers and Dispersed PolymersPrepared Above:Preparation of a Blend of Dispersed Oligomer dV2 and Dispersed PolymerP1=V2 P1

A1L 3-necked round bottom flask, equipped with stirrer and N₂-inlet, wasloaded with oligomer dispersion dV2 (60 g) in a nitrogen atmosphere. Tothis was added water (20 g) and vinyl polymer P1 (20 g). The mixture wasstirred for 30 minutes and stored under a nitrogen atmosphere. Theresultant dispersed blend V2P1 has a solid content of 25% by weight.

The oligomer/polymer blend dispersions listed in Table 5 below wereprepared using the method described above for V2P1.

TABLE 5 Components V2P1 V2P2 V2P3 V2P4* V3P5 V4P6 Oligomer code dV2 DV2dV2 DV2 dV3 dV4 Oligomer (g) 60 60 40 54.6 40 60 Polymer code P1 P2 P3P4 P5 P6 Polymer (g) 20.00 22.22 29.82 45.4 35.29 22.42 Oligomer (% ofsolids) 60 60 40 40 40 60 Polymer (% of solids) 40 40 60 60 60 40 Water(g) 20.00 17.78 30.18 — 24.71 17.58 Dispersion solids (%) 25.2 25.0 25.040.0 25.0 25.0 Components V5P7 V6P8** V7P9 V3U1P10 V2V4U2P11*** Oligomercode dV5 dV6 DV7 d(V3U1) DV2V4U2 Oligomer (g) 50 84.4 15 12/4913.9/6.9/48.0 Polymer code P7 P8 P9 P10 P11 Polymer (g) 33.78 15.6 47.2222.42 21.7 Oligomer 50 80 15 60 59 (% of solids) Polymer 50 20 85 40 41(% of solids) Water (g) 16.22 — 37.78 15.99 9.53 Dispersion 25.0 35.025.0 25.0 33.6 solids (%) Components V8P5 V8V2P12 Comparative V3P5Oligomer code dV8 d(V8V2) DV3 Oligomer (g) 50 28/28 7 Polymer code P5P12 P5 Polymer (g) 29.41 47.19 54.83 Oligomer (% of solids) 40 40 7Polymer (% of solids) 60 60 93 Water (g) 15.59 — 38.17 Additive typeAtlas G4809 ADH — (20%)/ADH Additive amount (g) 5.0/1.35 0.76 —Dispersion solids (%) 26.0 33.9 25.0 *oligomer dispersion is used at 44%solids **oligomer dispersion is used at 33.15% solids ***oligomerdispersions are used at 45.7% solids

EXAMPLE 1 Pigmented Paint Composition Comprising Oligomer Dispersion dV1

A 1I 3 necked round bottom flask equipped with a stirrer was loaded withdispersion dV1 (100 g) in a nitrogen atmosphere. TiO₂-based pigmentpaste C830 (30.78 g; solid content 72%), a flow agent Byk 344 (0.1 g),and a urethane thickener (Borchigel L75, available from Bayer, 50% inwater) were added and the mixture was stirred for 30 minutes at ambienttemperature and the resulting composition was allowed to standovernight. Before measuring the equilibrium viscosity and testing theproperties of the composition the viscosity of the composition wasadjusted to 4000 to 6000 mPa·s. using Borchigel L75 (50%).

Pigment paste C830 is formulated as TiO₂ (24.0 g), propylene glycol (2.4g), water (3.3 g), AMP95 (2-amino-2-methyl-1-propanol available fromlntergrated Chemicals bv, 0.2 g), Dehydran 1293 (defoamer additiveavailable from Gognis, 0.5 g, 10% in butylglycol), Surfinol 104E(wetting agent available from Air Products 0.4 g, 50% in ethyleneglycol) and Neocryl BT-24 (Acrylic emulsion polymer available fromNeoResins, Avecia BV, 3.1 g).

Further examples 2 to 14 and comparative example 17 were prepared asdescribed above with components as listed in Table 6. Example 15 wasprepared as a clear example with no pigment and in example 16 iron oxidepigment was used instead of C830 TiO₂. The drying characteristics andother properties of these examples are also presented in Table 6.

Water Resistance, Thumb Hard and Sandability Results

The thumb hard test result for Example 10 was 6 hours; Example 11, 5hours; Example 12, 6 hours; Comparative Example 17, 5 hours; ComparativeExample 18, 2 hours and Comparative Example 19, 1 hour.

The sandability test result for Example 9 was 24 hours; Example 10, 72hours; Example 11, 18 hours and Example 12, 24 hours.

Comparative Example 18 (C18)

P5 (150 g) was formulated with butylglycol (12.72 g) and thickened withBorchigel L75N to a viscosity of 4000 to 6000 mpa·s.

Comparative Example 17 (C17)

P7 (100 g) was used as prepared above.

TABLE 6 Example 1 2 3 4 5 6 7 Blend code dV1 V2P1 V2P2 V2P3 V2P4 V3P5V4P6 Blend amount (g) 100 100 100 100 100 100 100 Pigment paste 30.7830.78 30.78 30.78 49.24 30.78 30.78 C830 (g) pH 10.1 10.3 10.2 10.1 10.310.2 10.6 Open time (min) 55 60 55 60 50 56 55 Wet edge time (min) 30 1512 12 20 27 11 Dust-free time (min) 150 70 42 80 55 41 33 Tack-free time(hours) 19 18 5 18 5 4 1.5 Start yellowing 3.67 5.30 6.46 8.05 2.63 3.613.10 Dark yellowing 6.87 2.27 2.13 1.98 1.71 1.51 0.16 (Δb-dark)Daylight yellowing 4.33 0.40 1/37 2.83 2.40 0.64 0.40 (Δb-day) Example 89 10 11 12 Blend code V5P7 V6P8 V7P9 V3U1P10 V2V4U2P11 Blend amount (g)100 100 100 100 100 Pigment paste C830 (g) 30.78 43.09 30.78 30.78 30.78pH 10.1 10.4 10.4 10.3 10.4 Open time (min) 30 54 45 70 60 Wet edge time(min) 10 14 14 15 24 Dust-free time (min) 30 65 50 55 45 Tack-free time(hours) 5 8 5 5 5 Start yellowing 2.29 4.15 4.39 4.47 2.82 Darkyellowing — 3.30 1.90 2.06 1.84 (Δb-dark) Daylight yellowing — 1.48 0.461.41 1.12 (Δb-day) Example 13 14 15 16 C17 C18 C19 Blend code V8P5V8V2P12 V6P8 V7P9 V3P5 P5 P7 Blend amount 100 100 100 100 100 150 100(g) Pigment paste 30.78 30.78 — PW602 30.78 — — C380 (g) (1.2) pH 10.310.3 10.1 10.3 10.5 — — Open time 34 42 51 45 18 35 45 (min) Wet edge 1822 22 31 8 7 8 time (min) Dust-free 33 28 21 25 23 15 30 time (min)Tack-free 14 2.45 18 18 1.42 1.5 0.5 time (hours) min Start yellowing2.32 2.86 — — — — — Dark 0.47 3.13 — — — — — yellowing (Δb-dark)Daylight — — — — — — — yellowing (Δb-day)

Comparative Example 20 (C20)

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with 1-methoxy-2-hydroxy propane (MHP, 75.0gram) and heated under reflux at 120° C. A mixture of EA (74.7 gram),MMA (67.5 gram), M (90 gram), MPEG350MA (2.4 gram) and tert-butyl peroxy2-ethylhexanoate (tBPEH, 11.73 gram) was added over a period of 3 hours.During this period it was necessary to add additional MHP (100 gram) toreduce viscosity of the reaction mixture. Refluxing was continued for anadditional 15 minutes and a two additional amounts of tBPEH (1.5 grameach) were added to complete the polymerisation. The solution was cooledto 90–95° C. and allyl glycidyl ether (65.4 g) was added together withbenzyl trimethyl ammonium hydroxide (1.0 gram, 40 wt % in water). Thesolution was heated to 120° C. under reflux until the acid value hadfallen below 5 mg KOH/g solids. The solution was cooled to ambienttemperature. The water solubility and water and ammonia (12.5%)resistance of this oligomer were compared to those of example 4 (table6).

The water solubility was 91.9%. The water and ammonia (12.5%)resistances of this oligomer were compared to that of vinyl oligomer V2.The data is shown in Table 7 and 0=poor and 5=good.

TABLE 7 Oligomer water solubility (%) water ammonia Comparative Example20 91.9 3 1 Vinyl oligomers V2 4.2 5 5

The equilibrium viscosity measurements for examples 1 to 16 preparedabove was measured using a range of shear rates and the results areshown in Tables 8 to 22 below.

TABLE 8 Example 1 Shear rate Shear rate Shear rate Shear rate 0.0997 s⁻¹0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 38.39 7 5 4 3 10.0 40.38 12 9 5 4 15.0 41.30 3 7 6 4 20.0 42.95 2011 7 6 25.0 44.85 33 13 9 6 30.0 46.49 36 16 11 8 35.0 48.31 54 22 13 940.0 50.37 89 29 17 11 45.0 52.52 67 26 16 11 50.0 54.69 613 43 22 1455.0 57.24 185 45 22 14 60.0 59.52 579 68 34 18 65.0 61.76 555 68 31 1770.0 64.42 1000 236 115 — 75.0 66.67 1110 150 83 32 80.0 68.80 131004590 — — 85.0 70.49 61600 21300 — —

TABLE 9 Example 2 Shear rate Shear rate Shear rate Shear rate 0.0997 s⁻¹0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 39.11 5 6 5 5 10.0 42.01 3 7 7 — 15.0 45.11 9 4 6 5 20.0 47.04 2 6 74 25.0 50.48 9 6 7 4 30.0 53.00 11 6 6 5 35.0 56.38 8 8 6 5 40.0 59.6642 15 6 6 45.0 63.35 166 35 22 12 50.0 66.81 1270 247 51 — 55.0 69.895440 791 86 31 60.0 72.11 14100 2000 136 30 65.0 73.78 20100 3510 242 —70.0 74.82 31100 5690 452 115

TABLE 10 Example 3 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated Viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 39.71 12 11 6 6 10.0 41.21 10 10 8 6 15.0 43.56 9 10 9 7 20.0 45.436 11 101 8 25.0 47.81 27 13 13 9 30.0 50.93 41 20 15 10 35.0 54.13 27 2017 12 40.0 56.65 69 29 19 9 45.0 59.85 190 44 27 10 50.0 63.81 75 42 3011 55.0 67.35 285 39 27 10 60.0 72.57 2040 731 — — 65.0 75.75 11700 2580457 —

TABLE 11 Example 4 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated Viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 39.38 2 11 11 9 10.0 40.72 13 9 12 10 15.0 42.49 4 17 17 13 20.044.73 3 17 19 15 25.0 46.70 11 19 19 14 30.0 48.85 15 23 22 15 35.051.83 24 26 23 16 40.0 54.49 13 24 22 13 45.0 57.36 19 27 24 12 50.060.63 37 36 21 10 55.0 63.67 122 73 36 — 60.0 66.78 1260 651 302 21465.0 70.61 5610 2020 86 — 70.0 72.21 10900 3490 1260 229 75.0 74.4619600 7860 2320 —

TABLE 12 Example 5 Shear Rate Shear Rate Shear Rate Shear Rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (Pa · s) (Pa · s) (Pa · s) (Pa · s) 5.039.16 4 7 5 3 10.0 41.87 5 6 4 3 15.0 44.55 3 6 5 3 20.0 47.60 9 7 5 325.0 50.62 19 10 6 3 30.0 54.32 63 28 11 5 35.0 57.67 1230 200 44 1540.0 60.67 4160 621 125 14 45.0 63.62 15300 2390 248 47 50.0 66.46 253003990 353 161 55.0 67.84 38200 6510 659 254 60.0 69.43 59400 11100 1800 —65.0 70.63 65700 13300 1470 —

TABLE 13 Example 6 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 — — — — — 7.0 — — — — — 14.0 40.78 200 85 40 16 19.0 43.08 126 13 2813 24.0 45.71 188 117 49 3 28.0 47.93 126 84 45 6 33.0 50.99 817 257 64— 43.0 54.11 960 263 70 — 48.0 57.73 3090 877 269 — 53.0 61.31 4380 1510543 — 60.0 65.37 48700 10800 2570 —

TABLE 14 Example 7 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated Viscosity viscosityviscosity Viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 38.39 7 5 4 3 10.0 40.38 12 9 5 4 15.0 41.30 3 7 6 4 20.0 42.95 2011 7 6 25.0 44.85 33 13 9 6 30.0 46.49 36 16 11 8 35.0 48.31 54 22 13 940.0 50.37 89 29 17 11 45.0 52.52 67 26 16 11 50.0 54.69 613 43 22 1455.0 57.24 185 45 22 14 60.0 59.52 579 68 34 18 65.0 61.76 555 68 31 1770.0 64.42 1000 236 115 — 75.0 66.67 1110 150 83 32 80.0 68.80 131004590 — — 85.0 70.49 61600 21300 — —

TABLE 15 Example 9 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity Viscosityviscosity Viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 37.20 — — — — 6.0 37.77 43 30 11 5 10.0 40.14 — — — — 13.0 40.7290.6 61 25 5 18.0 43.61 70.8 49 20 5 24.0 45.61 239 175 55 — 30.0 48.22191 144 47 8 35.0 50.90 246 195 70 1 40.0 53.65 434 182 67 1 45.0 56.71243 168 74 2 50.0 59.93 294 168 73 9 56.0 63.41 2920 445 86 — 62.0 66.274430 557 90 22

TABLE 16 Example 10 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)5.0 39.38 35 24 17 — 10.0 40.44 3 20 20 15 15.0 43.09 11 25 22 13 20.045.52 27 32 27 12 25.0 48.17 91 51 35 9 30.0 51.30 163 55 41 12 35.054.97 197 88 56 14 40.0 62.50 298 122 54 13 45.0 63.00 367 127 55 1250.0 67.45 2650 771 161 55.0 71.43 2090 568 114 20 60.0 77.02 9870011900 1490 —

TABLE 17 Example 11 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids Viscosityviscosity viscosity viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 5.0 39.09 12 10 6 4 10.0 40.26 9 15 9 6 15.0 42.25 16 16 10 5 20.044.00 39 25 14 6 25.0 45.90 34 26 15 5 30.0 48.28 53 25 14 7 35.0 51.1654 26 13 9 40.0 53.38 59 26 16 8 45.0 56.00 133 39 16 9 50.0 59.34 13339 16 9 55.0 62.10 162 39 15 9 60.0 65.81 174 40 15 10 65.0 67.69 341363 23 13 70.0 69.84 703 131 43 9 75.0 71.63 4410 994 127 —

TABLE 18 Example 12 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids Viscosityviscosity viscosity Viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 5.0 38.98 14 4 2 1 10.0 40.65 11 5 2 1 15.0 42.98 12 2 2 2 20.0 45.4211 2 2 2 25.0 48.09 4 4 3 3 30.0 50.43 19 9 5 4 35.0 53.25 55 19 8 540.0 55.87 103 34 13 8 45.0 60.90 304 74 20 8 50.0 62.08 931 156 34 655.0 64.23 7690 1500 36 — 60.0 67.30 17800 3030 120 2

TABLE 19 Example 13 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids viscosityviscosity viscosity viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 2.0 38.30 20 0.3 1 1 6.0 39.50 2 1 1 1 10.0 41.00 5 1 2 1 15.0 42.805 3 3 2 20.0 44.20 3 4 3 2 25.0 46.03 10 7 5 3 30.0 47.08 2 8 6 4 35.049.80 3 13 9 5 40.0 51.50 3 22 13 7 45.0 53.50 93 39 18 10 50.0 55.40232 75 33 9 55.0 57.40 1150 182 49 7 60.0 59.80 5780 1270 — — 65.0 60.9014700 4760 — —

TABLE 20 Example 14 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids viscosityviscosity viscosity viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 2.5 49.30 9 13 10 — 7.0 50.90 63 39 21 9 10.0 52.40 51 40 22 96 15.053.80 145 75 41 9 20.0 55.70 111 82 43 11 25.0 57.60 236 168 87 16 30.059.40 338 196 95 3 35.0 61.40 657 404 — — 40.0 63.20 1150 77 368 19 45.065.10 4070 3070 — — 50.0 67.30 10100 6170 1690 22 55.0 68.90 41500 119001400 32 60.0 70.60 88600 18400 457 —

TABLE 21 Example 15 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids Viscosityviscosity viscosity viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 0.0 35.00 — — — — 3.0 44.50 47 16 7 4 8.0 48.40 55 20 9 4 16.0 52.6090 28 16 2 21.0 57.10 101 34 22 1 26.0 62.80 174 107 53 5 32.0 67.60 187119 49 1 38.0 72.80 172 130 81 — 44.0 77.60 71 109 78 11 50.0 80.30 6742 31 42 56.0 84.00 806 216 84 43

TABLE 22 Example 16 Shear rate Shear rate Shear rate Shear rateCalculated 0.0997 s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Solids Viscosityviscosity viscosity viscosity (min) (%) (Pa · s) (Pa · s) (Pa · s) (Pa ·s) 0.0 40.00 — — — — 4.0 42.80 110 17 10 — 10.0 45.10 63 18 13 7 16.052.00 119 39 22 7 21.0 55.20 79 4 9 8 28.0 58.40 360 114 46 6 33.0 62.20346 104 44 4 39.0 66.10 1520 289 65 6 44.0 70.50 1170 251 66 — 51.073.90 776 234 31 6 56.0 77.00 1330 236 39 4 64.0 78.80 6900 — — — 67.079.60 25700 4410 — —

TABLE 23 Example C18 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 41.74 506 104 16 3 9.0 46.28 1465 341 59 13 14.5 50.99 5043 1334 30551 23.0 59.16 16240 5356 910 193 29.0 65.50 22290 12750 2040 448

TABLE 24 Example C19 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0. 22.20 68 28 10 3 5.0 24.03 120 56 18 4 12.0 26.54 1156 422 82 15 18.028.93 5804 1588 212 33 24.0 31.81 8118 2073 289 69 31.0 36.13 12560 4273568 116 38.0 41.88 12720 3278 415 78 44.0 48.27 33020 8738 1087 186

1. An aqueous coating composition comprising an ambient temperatureself-crosslinkable water-dispersible vinyl oligomer(s) having a measuredweight average molecular weight in the range of from 1,000 to 80,000Daltons and dispersed vinyl polymer(s) and 0 to 25% of co-solvent byweight of the composition where the ratio of said self-crosslinkablevinyl oligomer(s) to the dispersed vinyl polymer(s) is in the range offrom 90:10 to 10:90 and said dispersed vinyl polymer(s) has a measuredweight average molecular weight ≧90,000 Daltons and wherein saidcomposition when drying at ambient temperature crosslinks to form acoating that has the following properties: i) an open time of at least20 minutes at 23+/−2° C.; ii) a wet edge time of at least 10 minutes at23+/−2° C.; iii) a tack-free time of ≦20 hours at 23+/−2° C.; and iv) anequilibrium viscosity of ≦3,000 Pa.s, at any solids content when dryingin the range of from 20 to 55% by weight of the composition, using anyshear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; andwherein said self-crosslinkable water-dispersible vinyl oligomer(s) is≦60% by weight soluble in water throughout a pH range of from 2 to 10.2. An aqueous coating composition according to claim 1 wherein saidself-crosslinkable water-dispersible vinyl oligomer(s) has a solutionviscosity ≦150 Pa·s, as determined from a 80% by weight solids solutionof said self-crosslinkable water-dispersible vinyl oligomer(s) in atleast one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.
 3. An aqueous coating compositionaccording to claim 1 wherein said self-crosslinkable water-dispersiblevinyl oligomer(s) has a solution viscosity ≦250 Pa·s, as determined froma 70% by weight solids solution of said self-crosslinkablewater-dispersible vinyl oligomer(s) in a solvent mixture consisting of:i) at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof; ii) water andiii) N,N-dimethylethanolamine; where i), ii) and iii) are in weightratios of 20/7/3 respectively, using a shear rate of 90±5 s⁻¹ and at23±2° C.
 4. An aqueous composition according to any one of claims 1, 2or 3 wherein said composition has an equilibrium viscosity ≦5,000 Pa·swhen measured using any shear rate in the range of from 0.09±0.005 to90±5 s⁻¹, and an equilibrium viscosity of ≦3,000 Pa·s when measuredusing any shear rate in the range of from 0.9±0.05 to 90±5 s⁻¹, and anequilibrium viscosity of ≦1,500 Pa·s when measured using any shear ratein the range of from 9±0.5 to 90±5 s⁻¹, at any solids content whendrying in the range of from 20 to 55% by weight of the composition andat 23±2° C.
 5. An aqueous composition according to any one of claims 1,2 or 3 wherein said composition has an equilibrium viscosity ≦5,000 Pa·swhen measured using any shear rate in the range of from 0.09±0.005 to90±5 s⁻¹ after a 12% increase of the solids content by weight of thecomposition when drying.
 6. An aqueous composition according to any oneof claims 1, 2 or 3 wherein the self-crosslinkable water-dispersiblevinyl oligomer(s) has a PDi≦15.
 7. An aqueous composition according toany one of claims 1, 2 or 3 wherein the self-crosslinkablewater-dispersible vinyl oligomer(s), when a precursor vinyl oligomer(s),has a measured Tg in the range of from −90 to 100° C.
 8. An aqueouscoating composition according to any one of claims 1, 2 or 3 comprising:i) 15 to 40% of a crosslinkable oligomer(s) by weight of total bindersolids of which at least 52 wt % is said self-crosslinkablewater-dispersible vinyl oligomer(s); ii) 0 to 10% of a non-crosslinkableoligomer(s) by weight of total binder solids; iii) 50 to 85% ofdispersed vinyl polymer(s) by weight of total binder solids; wherei)+ii)+iii)=100%.
 9. An aqueous coating composition according to any oneof claims 1, 2 or 3 additionally comprising a pigment.
 10. An aqueouscomposition according to claim 1 wherein the dispersed vinyl polymer(s)has particle size in the range of from 25 to 1000 nm.
 11. An aqueouscomposition according to claim 1 wherein the dispersed vinyl polymer(s)has an acid value below 160 mgKOH/g.
 12. An aqueous compositionaccording to claim 1 wherein the dispersed vinyl polymer(s) iscrosslinkable.
 13. An aqueous composition according to claim 1 whereinthe dispersed vinyl polymer(s) has a measured Tg in the range of from−50 to 300° C.
 14. An aqueous coating composition according to claim 1comprising: i) 0 to 15% co-solvent by weight of total binder solids; ii)35 to 65% of said self-crosslinkable water-dispersible vinyl oligomer byweight of total binder solids; wherein the self-crosslinkablewater-dispersible vinyl oligomer(s) comprises 45 to 75 wt % of fattyacid groups; and wherein said dispersed vinyl polymer(s) has an acidvalue below 20 mgKOH/g.
 15. An aqueous coating composition according toclaim 1 comprising: i) 3 to 26% of a crosslinkable oligomer(s) by weightof the composition of which at least 52 wt % is said self-crosslinkablewater-dispersible vinyl oligomer(s); ii) 0 to 6.5% of anon-crosslinkable oligomer(s) by weight of the composition; iii) 10 to56% of dispersed vinyl polymer(s) by weight of the composition; iv) 0 to15% of co-solvent by weight of the composition; and v) 5 to 65% of waterby weight of the composition; where i)+ii)+iii)+iv)+v)=100%.
 16. Anaqueous composition comprising an ambient temperature self-crosslinkablewater-dispersible vinyl oligomer(s) having a measured weight averagemolecular weight in the range of from 1,000 to 80,000 Daltons and adispersed vinyl polymer(s) and 0 to 25% of co-solvent by weight of thecomposition where the ratio of said self-crosslinkable water-dispersiblevinyl oligomer(s) to said dispersed vinyl polymer(s) is in the range offrom 90:10 to 10:90 and wherein said composition when drying at ambienttemperature crosslinks to form a coating having the followingproperties: i) an open time of at least 20 minutes at 23+/−2° C.; ii) awet edge time of at least 10 minutes at 23+/−2° C.; iii) a tack-freetime of ≦20 hours at 23+/−2° C.; and iv) an equilibrium viscosity of≦3,000 Pa·s, at any solids content when drying in the range of from 20to 55% by weight of the composition, using any shear rate in the rangeof from 9±0.5 to 90±5 s⁻¹ and at 23±2° C.; and wherein saidself-crosslinkable water-dispersible vinyl oligomer(s) is ≦60% by weightsoluble in water throughout a pH range of from 2 to 10 and wherein thedispersed vinyl polymer(s) has a measured weight average molecularweight ≦90,000 Daltons with the proviso that the dispersed vinylpolymer(s) has a solution viscosity >150 Pa·s, as determined from a 80%by weight solids solution of the dispersed vinyl polymer(s) in at leastone of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.
 17. An aqueous coating compositionaccording to claim 1 or claim 16 wherein said self-crosslinkablewater-dispersible vinyl oligomer is self-crosslinkable by autooxidation,Schiff-base crosslinking or a combination thereof.
 18. A coatingobtained from an aqueous composition according to any one of claims 1, 2or
 3. 19. A method of coating a substrate which comprises coating thesubstrate with an aqueous coating composition according to any one ofclaims 1, 2 or 3.